this is (in my opinion) the best place to start watching this, you also need slade, a drawing program, and some LUA experience if you wanna make custom moves cause this video doesnt teach that part and im still trying to learn that part. for learning LUA i made a page asking about that and if you scroll the very bottom you can find all the info you need
https://mb.srb2.org/threads/where-to-start-with-learning-srb2-lua.35245/ i hope this helps have a good day!