What class/setup should I use?
Mostly I folllow the general code which is one tank one artillery and one infantry but mix it up its after all your choice

The commanders I mostly use are:
Soviet Reserve Army
Soviet Shock Army
Shock Rifle Frontline Tactics

What is my first move?
well your first move is totaly up to you. You can choose what you want to begin with this can range from either building a support kampanye etc.

What do I do next?
Well, this is where it gets tricky - First of all you must accomplish these objectives as fast as you can. You can accomplish these objectives in any order.
1. Build mortars and maxim machine guns.
2. Acquire at least 1 Fuel Point.
3. Make as many fuel caches as possible.
4. Build at guns and katyusha rocket launchers.
5. Build heavy tank destroyers or T-34s

Now that you know how to begin and what to strive towards this is how you should use your tactics and arsenal in game

From the beginning start building conscripts and 1 engineer squad
Now that you have at least one conscript squad start capping as many points as possible by doing this you will force the enemy to spread their forces and remember one conscript squad outnumbers one grenadier squad. Now you should mostly avoid contact with the enemy but if they are creeping in your territory you should use your forces wisely

What to do if you built an support company
Firstly build mg squads to cover the victory and feul points that you have captured(if possible gather them in a building) then build mortars to destroy any enemy mg squads
mg squad:maxim machine gun supresser infantry weak against mortar fire
mortar:powerfull long range artillery weak against infantry and scout cars slow

What to do if you built an infantry company
Build the cheap scout car to mow down infantry and even mg squads(beware mg squads still do damage against scout cars) and mortars. The scout car is most effective when transporting a sniper squad because snipers are a one shot kill but soviet snipers are two men squads use this to your advantage

After you have reached command point one try to build anti tank building to annoy the enemy with a katyusha you will need a lot of feul

The katyusha will obliterate enemy defenses infantry and at guns shoot mostly the rocket at heavily defended areas as well as areas with a large number of enemy troops present

This is the most difficult aspect of the soviets it has the following negative effects
weak armor
dont last long
arent very durable tanks

But there are some positive aspects
fast agile
t34 has ram ability
cheap to preduce
you can spam hundreds of them

When you come in contact with a enemy tank(except tigers) you should mostly keep your t34 safe unless you outnumber them rather use at guns at grenades or gaurds rifle infantry to blind them even use anti tank destroyers like the su 85 (beware they are expensive)
Do not use the ram ability unless you are in a dire situation

how to deal with a tig er?
Now this is a very difficult task for at guns do not do much damage against a tiger t34 are almost useless unless you have over 3 but they will easily be destroyed by a tiger. So what you should is make su 85 (over 2) and the mighty Is2 if you can. The Is2 has powerfull front armour and a mighty powerful gun but you should only face a tiger head on with a Is2 this tank is weak on the sides and the tank same thing goes vice versa with the tiger so i would recommend hitting a tiger from the side

Enjoy and remember to always have fun