I have a doubt about using only SDL2 to make my first 2D game and I am new in this business of creating games, but I don't know if it really is a good practice to use in my future games.

Beginner questions:

Is it good to use only SDL2 for my own game engine?

Should I use OpenGL or other bookstores (SFML, DirectX, ...)?

Should I use a game engine already created to make my games (Unity, Unreal, ...)?

What do I advise as a novice game creator?

juliocesardev said:
Is it good to use only SDL2 for my own game engine? Should I use OpenGL or other bookstores (SFML, DirectX, ...)? Should I use a game engine already created to make my games (Unity, Unreal, ...)?

Depends on your interests and goals.

Is your main priority making and finishing games? Do you like to create art and coding for gameplay? In that case, Unity or Unreal are good matches. They allow you to make quick prototypes, and are going to take lots of chores from you in the long run while finishing your games.

If you are more of a technician, take joy from programming more so than the art of game-making, then you might take more enjoyment out of working more low-level with one of the APIs/frameworks you mentioned. From a pure productivity-standpoint, I wouldn't recommend it though, unless your games are really simple and don't require much content (=> 2d doesn't automatically mean simple to me), then you are going to be quite a bit slower than just booting up unity, and having everything given for you. Other reasons for avoiding major engines might be very specific requirments that are not handled well in those engines, but I doubt you are at that point.

Hope that gives you some pointers for what to decide on.