RR, Basically:
The gmf file(s) supplies the 'objects' in an arena.
The python enables the 'dynamics' in the arena.
So these 2 are the main things to learn.
GMF: CB/FB have several nice tutorials that would help you, as they did me. Be patient and it will come together:
Tutorials.
Python: The Python you can read up on or ask. I have a work-in-progress 'Reference Sheet' for RA2 commands if you'd like that.
It's allot of fun to make new components and arenas in RA2, and there's allot of new stuff that could be done still.
Here are some arena ideas:
Arena Ideas.
..