First I learned how to program in c (recently I learned c++). Then I learned how to read assembly, how pc memory works, what is dynamic and static linking, what are vtables, and for debugging I learned how to use tools like ghidra, Detect It Easy, xdbg, etc…
Learned about compression, un/packing, dll injection, anti-debug methods.
Also did some simple game hacking, nothing fancy.
It’s not all but I can’t write everything here… I don’t know any good RE courses (maybe someone else here can share).
I also read a lot of writeups on reddit from r/ReverseEngineering and r/REGames