Well, it really depends what you’re doing. Gamemodes incorporate a lot of things that you can learn from SWEPs, SENTs, and just code in general. I started by editing other people’s gamemodes and observing other people’s code, but that’s only because people starting to learn when I was learning didn’t have the godsend that is known as our GMod Lua Wiki.
A lot of people here don’t seem to realize how lucky they are to have any documentation at all. Like I said, a lot of the “Lua Gods” as you call them had to start off by just looking at other people’s code, but if we had had access to a wiki we would have rushed over there immediately.