The key is when, for what, and how much to pay.

Almost f2p games have pay to win system.
Paying for a better car or a more powerful gun will give you a better chance of winning.
So is this game.

So, for players who want to enjoy 4Story, I would like to share with you what I know about when to use cash and what to expect.

Before level 30, there is virtually no problem with progressing through quests, etc., even without using your credit card.
However, if you want to progress a little faster, you can purchase level 38 gears and upgrade it to +12 to play as a very powerful character against monsters.

However, the PvE content of this game may have been fun 10 years ago, but it is not like that now. It is simple and boring.
It would be like a monk's asceticism to progress to level 30 while only playing PvE content.

But... Fortunately, after completing the introductory content of about 10 minutes and selecting a country,
you can participate in "Territory War" regardless of your level (If your level is low, your stats will be adjusted). In this "Territory War" you can see the real 4Story.
The real appeal of 4Story lies in PvP through cooperative play with party members consisting of various classes. It's very fast and exciting.
(You can check the "Territory War" schedule in the "War Info" tab of the "Guild Window" ('G' key)).
In addition to "Territory War," there are also small-scale party battle contents such as "Mission War".
And in order to enjoy these contents smoothly, I strongly recommend joining a guild and actively interacting with other players.

Anyway, to fully enjoy these contents, you will need the devil's "Gear Upgrade" and this content will threaten your credit card.
The highest Upgrade level is +24 at the moment, and it seems that it can be classified as follows.

+1 ~ +11 : Not expensive, It's a little weak to enjoy this game.
+12 ~ +15 : So so..., Something is a bit ambiguous.
+16 ~ +18 : A little expensive... I'll wait for the upgrade event... these levels would be nice to enjoy this game at the moment. some times win some times defeated.
+19 ~ +24 : Crazy !!! I'll try it once in a while, with the same mindset as buying a lottery ticket. +24 can't be had with just a credit card. It requires God's blessing.

And I will share with you the top secret of the "Gear Upgrade" system that almost old players know.
The secret is in the following numbers.

+1, +2, +4, +6, +8, +10, +11, +13, +15, +17, +19, +21, +23

The above numbers are the "Gear Upgrade Levels" that have a relatively high success rate for "Gear Upgrade".
That means upgrading +14 gear is not a good idea. To upgrade +14 Gear, it is advantageous to first use a "Purification Scroll" to make it +13, then upgrade it to +15. And you should increase the upgrade level by +2 at almost every level.

To perform "Gear Upgrade" in 4Story, you will need a "Rare Upgrade Magic Scroll" or "Upgrade Magic Scroll".
As stated in the item description, "Rare Upgrade Magic Scroll" will increase the "Upgrade Level" of the item by +1~+3 upon success,
while "Upgrade Magic Scroll" will increase the "Upgrade Level" of the item by +1 upon success.

As I mentioned before, the upgrade level needs to be increased by +2, so unless there is a special situation, you should use the "Rare Upgrade Magic Scroll".
In fact, the "Upgrade Magic Scroll" is almost useless.

While I'm at it, I'll share a few more details.
The success rate of "Gear Upgrade" at :

+1, +2, and +4 : Almost 100%.
+3, +6, +8, and +10 : Almost 100% when using "Potion of Fortune" or during "Upgrade Event".

In other words, you can upgrade up to +11 without failure. Also, if you use "Protection of Upgrading", which is essential when upgrading, the upgrade level will not go below +11, so the actual upgrade range is from +11 to +24.

+11 : I think... 50% or higher when using "Potion of Fortune" during "Upgrade Event".
+13, +15 : I think... around 50% when using "Potion of Fortune" during "Upgrade Event".

If you successfully upgrade from +15, it will be +16~+18, and as mentioned earlier, +16~+18 would be nice to enjoy this game.
Of course I really want +24 too, but it is not necessary to enjoy this game. In 4Story, the teamwork of the party can defeat +24.
Every class in 4Story has at least one stun skill. If the teamwork of the party is good and there is only one opponent, the opponent will be defeated without being able to do anything even if he has a full set of +24.
Even in a duel between parties, the teamwork can be a relatively more important factor.
The Priest's "Sublime Pain" skill protects the surrounding party members from any attacks as long as MP allows.
The Warrior and Archer's "Smash Chest" and "Destroy Weapon" skills temporarily nullify the opponent's Gears.
The Wizard's "Flame of Hell" skill destroys enemy formations by scattering enemy party members and causes an area stun effect.
And there are many elements that enable efficient combat through complementary effects between classes or that can neutralize enemy characters or the gears they are wearing.
So the teamwork of the party is often more important than the upgrade level of the gear.

In conclusion, the most important thing in this game is to join a guild, meet many friends, form a good party, and play together. I think that is the most enjoyable way to play this game.

Perhaps the following course is good way to enjoy this game.
1. Purchase a level 38 gear set and upgrade it to +12 or so. (Of course, you must play the introductory content and complete the country selection.)
2. Join a guild and enjoy PvP content such as "Territory War" and craft level 44 gears through PvE content. (Playing only PvE content? That's not a good idea if you are not a monk.)
3. After obtaining 44 gears, upgrade them to +16 or higher.
4. Enjoy playing with your guild members. And adding magic options to your gears using the "Refinement" feature.

And... be careful, devil guys in zemi are always targeting your pockets. XD
Good luck !