Also event-driven programming. (especially the idea of delaying effects, e.g. so in an RPG someone can perform a Reaction which disables the effects of an Action performed by another character before they’re applied).
Learn about stacks.
When you’re ready to make your brain bleed a little, try designing on paper the data structure to make D&D turns work.
Hints: player initiative is a circular array, reactions are a stack, actions/reactions are events. Actions are events which modify characters, reactions are events which modify other players events.
Ignore abilities which e.g. create new terrain or whatever. Ignore movement, positioning, targetting entirely.
This will be fun!
Also I can recommend the free book Game Programming Patterns. It’s useful for programming concepts even if you don’t make games