I hear a lot of first time players struggling with the AI, and I can assure you that they are beatable, and you should not feel bad for struggeling with it on your first few games (I know I did).
This guide will also re-iterate on some stuff from the last guides, as well as add quite a few PVP tips for veterans of the game.
Note that there is not really a Meta yet because of a lack of games, so take the most specifics with a grain of salt.
A huge grain of salt, as the Meta changes every other game...

Uncrewed lets you make your own units. With so many possiblilities I can't tell you the optimal sollution to what a unit should be, or which units go into an army. The only thing I can do, is tell you what goes into my armies. Take this advice with a pinch of salt.

The first thing you should do is download this amazing creation:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1221594255
It is the groveller form Randomnumbers(I love him for making this) and it is by far the cheapest most usefull miner you can get (it's even amphibious!). The only downside is it's low HP, so you can opt for something heavier later in the game. This will give you the economy boost yoou need to be faster than your enemies.
Building something bigger often means investing in something that will get obsolete quite fast (low HP and miniguns or revolver cannons will already perform poor in early mid game). It can give you an edge in raids, but I prefer investing in one medium 1 sized unit to defend.

There are a bunch of 1 wheel harvesters that are as cheap as you can get. These are bellow 100 pellets, speeding up your early game significantly, the only downside is that they are not amphibious. https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1824098771&searchtext= This one was made by Vulkan. There are more 1-wheel miners but this one outperforms the others. Although stability and power settings can be further optimized for extra performance.
Tip: there is something called the "linear build mode". This mode is the old way of constructing vehicles but is sometimes used by players to decrease the build speed by quite a large margin. I (Lanceraad) personally don't like it, but some other players do.

This is the first unit you get, the campaign and every skirmish starts you out with it (note, it does not count towards your popcap). I like how scrappy it looks but it's usefullness is questionable. It has too low health for an effective attacking unit (not mentioning the appaling damage one gatling gun or worse, one plasma thrower does) and it's too expensive for an early game miner. It's top heavy, and rolls over in tough terrain and it's underpowered with only one battery and 4 wheels draining energy (the groveller will last twice as long with only two screws).
The plus sides are its magnet and its manouverablility, but that won't get it very far. I highly reccomend adapting or replacing this unit.

I will use these stats for units throught the guide. I follow this pattern a lot.

So what should your army consist of? Again, what you want it to consist of, but there are a few essentials:

The Early game is the part of the game where you build up your harvesters, set up early defences and perform very early raids.

When the game starts you can crank 3 cheap harvesters out with the first boost from your factory if you time it just right with the first harvester the game gives you. Then continue to build these untill you have about 6/7.(Sometimes lesser if you feel danger.) One on the Heavy Pellets should suffice (2 if you need it for a tech rush,once labs finished you can let they harvesting normal pellets).
Now this will be fragile, and eassily targeted by raids, but it will give that early game boom in funds to get there the fastest with the mostest.

After this you should tech up to a maximum of 3 labs (one being the armory) and build your early defence unit. I defend with a medium 1 sized unit that has a Large Rotary or Revolver Cannon or 2 plasma guns (the long ones). Other weapons of similar DPS are also possible, but rockets or lasers might be hard to tech up to right away. If you want to use the normal rotary and revolver guns you might want to have 3 or 4 on this vehicle for the sake of DPS.
This is around the time the AI comes, and this unit should chase them off quite well for their first 3 raids or so. Making a repair pad/bay somewhere near the frontlines is not a bad decision right now. As is not having your unit on agressive stance.
It's generaly a bad idea to chase after the enemies with your defence unit, since you need it for defence. Unless you are fighting just one enemy, then you can raid immediatly.

Since the weapons I just mentioned require a propulsion lab, you can make a flying unit right now to attack with. This flying unit should have roughly the same specs as the defender. Attacking right now will win you the initiative against players, and set them back in terms of recources.
Always go for the harvesters first, and finish the kill. Retreat the unit once it's at 25% health, repair it and go at it again.
If your opponent defends it's harvesters heavily, you should attack their buildings in the following order:

• Construction towers building something
  
• Rocket Lab
  
• Laser Lab
  
• Propulsion lab

This is roughly the end of the early game and you should make a plan right now about what weapons you want to use, build a Laser Lab or a Rocket Lab to get top tech for one of these, the other will come later (Note, you don't have to use all weapons in the game, if you have a strategy that works with fewer labs, go for it!).
Build a few more harvesters, I usually aim for about 7-10 grovellers. This will usually stay the same throughout the match.

Most RTS players will already know this, but for those that don't:
Sometimes if you want to perform a rush attack, you can build 3-4 cheap harvesters. Do spend your resources as soon as you have enough!
Use hotkeys for lab or unit construction, and boost the factory(B) at the points where it will speed up production the most.
It's good to set control-groups by pressing CTRL + a number key. Putting your harversters in one group for quickly running away, your main base for build speed and your various groups of attacking units.

The mid game usually revolves around building an army that can defeat your enemies in the late game. If you are fighting against one player you might even be able to end the match right now.

If this is a free for all or team game, you could start setting up a base defence. Get an anchor point close to the harvesters and add a defensive unit. The anchor will let the unit attach itself to the point and get resupplied from there. You only have to add one battery on this unit regardless of weapons to save on costs (it's going to get recharged anyway). Adding a large rail gun will allow defensive units to help each other (due to range), but make them more vunerable to EMP. Adding EMP to defensive units will allow them to better deal with arial raiders.
I usually prefer the alternative of having combat vehicles that can mine or just placing tanks and other vehicles close to my valuble stuff.

Now there are a lot of RTS players that love to turtle, and with artillery emplacements (using the anchor) shooting over walls and a few EMP's for AA you can make a formidable defence. The AI will usually go for powerfull air units (if they have them in their repository) so this won't work wonders, but it should be good against a ground army.
However, I would not reccomend turteling against players. By turteling you will give the other player the initative. If he likes raiding you give him/her the choice to attack when and where he or she wishes. They can also freely expand wherever they want uncontested, which is game losing for you on a map like the shore, where there is only one expansion point.
If the opponent decides to go after your harvesters the way I described, you will lose at least a few. Losing 3 grovellers means losing 333 resources + the resources they would have collected in the time it takes to rebuild them. This is probably the value of a medium 1 sized unit, and this can be deciding in the early/mid game.
If you don't come out of your base, and the enemy keeps up the pressure with effective raids, you will get steamrolled quite quickly.
Even worse is that his or her mobile army will be bigger because you've put everything in static defence. So an attack might be quite difficult since you can't put your full force behind it. Even if you did not get raided, your army will still be behind in points.
And lastly, where will your defence go if your pellets run out and you have to move your harvesters?

Oh and a wall without defence is just a waste of pellets and time, the enemy only has to destroy one section to get through. Only if it delays them long enough for forming up a defence is it decent, but I doubt it.

In an AI match you can turtle, it will be fine. In a PVP match I strongly reccomend attacking as soon as you have something worth attacking with (don't leave your base completely exposed though, especially if there are more players on the map).
Again go for their harvesters (weakest first), this will make you regain the initative and put the other player back in resources.
Put some EMP in your defence if you are facing arial raiders, this will ground them and might stunlock them long enough for you to kill them.

Attacks/raids are common in the mid-game against players (or it's a free for all and no-one dears exit their base). Ideally you should keep up the pressure, this alone might win you the game.
Flying units are excellent for these types of attacks, as you should not be throwing away units against your enemy. Sometimes you need to cut your losses and withdraw.
Defenses will be getting more prevalent, so attacks should be planned out a bit better.
1. Attack the harvesters.
Usually the first target of any attack, harassing the resource line will get you ahead in the game. This should also be the best defended part of the base. And trading an expensive aircraft for a cheap miner is not worth it.
2. Attacking the buildings
Labs are usually not well defended, and can be really annoying if destroyed. Always go for the most expensive first (rocket lab), and work your way down. Armories are rebuilt too fast and are too cheap to have any impact.
I don't recommend attacking the main factory, as it has way too much health for an effective assault. You can attack it if you mostly defeated your opponent, but they are hiding somewhere.
3. Two-front attack
Only use this if you are good at strategy games, and are confident your units won't roll over without supervision. A two front attack is really hard to pull off. And Uncrewed's clunky units won't help much, but if you can pull it off, you probably should.
4. Feint Attack
Most maps have multiple ways of entering a base. And a lot of maps have space behind the base for aerial attacks. Making a small attack in one area, and then attacking somewhere else with your main force can be quite beneficial.
Ideally you should have your units all firing on their opponents rushing back one by one, or taking out their harvesters when their units are away.
Be careful that you don't divide your units up too much though, you don't want to get divided and conquered!
5. Hold out for a bigger unit
If you think you can get away with it, it might be better to invest in a late-game knockout. Uncrewed favors the bigger units (up to a point). So saving for a bigger unit might be a good idea.
In free for all's, or games against the AI this is more effective.

I'm so sorry, but the meta has been thrown around so much that I can't reccomend any one build order. As of the time of writing, going for large weapons (railgun, cannon, rocket launcher) seems to be a good idea.
You probably won't need to expand in the mid-game quite yet, but watch your harvesters and come up with a plan for expansion.

If you decide to make airial raiders, note that the heavy recoil of large weapons or railguns has little impact, making those weapons ideal. Rockets or Pulse Lasers (pulse lasers can't miss) are also good weapons.

This is also the point EMP weapons start ariving in game

Your raiding party should be finished by now, or already underway to your enemies. These units should never engage the main army, but focuss on the mining operation of your opponent. If the miners are too well defended, go for their buildings and hit the most valuable first (Rocket Lab or Laser Lab).
An AI player will be set back by this and a human player might totally lose the initative and dig in.

Initiative is something quite important in PvP, because if you are the only one raiding, and the other side is turteling, you will always fight on your terms. You can freely expand around the map and focuss entirely on annoying the other player untill you have sufficient units to strike.

If your strike went extremely well, you might just want to make a couple of medium 1 or medium 2 tanks and end the match right then and there.
If not, you should try and get more labs as required and start seeing if your income warrants another factory.

Usually it's cheaper/ easier to add armor than DPS, allowing bigger units to win matches. From here you should start producing some kind of mainline unit, depending on strategy. I usually go for either light or medium. The ai's campaign opponents have far less HP for similar units.

If you are playing against AI you should not expand until you are certain you can secure the next location (and it's simplest to just wait until your recources run out, the AI always finds your expantions), but if you are playing against humans you might want to look for a sneaky expantion far away from your base. Uncrewed maps are huge, and expantions are quite cheap, so this should be good strategy.

The mid game ends when you have all labs you need and have two factories producing a bigger army.

At this point, you've got it all. but your enemies do too. If you performed frequent raids well you should be winning, but if you decided to turtle your enemies will be quite strong.
The AI has a ton of flying units at this point, and made ample use of rockets allong with all other weapons. It's about time to attack, and you should be prepared.
Its at this point in the game that EMPs will start to play a big role. AI won't use them unless they are on hard, but players might spam them. Your raids should be getting less effective due to this.

Your vehicles should be able to hit air, and you either have a heavy emphasis on energy weapons or you brought EMP's along. An assault on a base is going to take a while, so make sure you pack enough ammo/energy to do the job. It's not a bad idea to have a few heavies with you to act as spearhead.
If it is a free for all, ALWAYS avoid getting in between two enemy armies. And as a general rule, you won't win any match with battles in the middle of the map. You should try to go to the enemy base as fast as possible (only engaging to avoid casuallties)
If a player has been turtelling hard, you should capture a few pads outside his base to resupply your units. Sending reinforcements across the map is going to take a while.

Your target is the enemies economy, park your army on top of their recource operation and bleed them dry. If they don't bite leave a few units there and proceed to wreck their base. Always look at the closest expantions. The AI never makes a sneaky expantion, players might.

If the AI is undefeated but no longer producing untis, they may have some unit stuck somewhere. Check any water with corners or steep ramps. If you destroy the opponent's main base, their units will become visible.

Thanks to Cyan for contributing to this guide!
And also a thank you to Cyan for completely reinventing the meta every single game so that this guide will be out of date the moment it is released!

Also great thanks to the Uncrewed community, without their creativity, this game wouldn't be where it is today.

And of course, thanks to the Dev for making such a good game!