Where to start drawing characters and backgrounds for 2D games?

Question

2D

Hello Toasters. I currently draw in SAI. There is a great desire to learn how to draw characters, backgrounds, etc. for 2D games on iOS, Android, PC.
The question is small, where to start. Are there special programs in which it is necessary to draw or can you also do everything in SAI.
Maybe someone has good courses on 2D characters, etc.
Thanks in advance.

Answer 1

And silence :(