Lua

You can check out Code Blue on youtube. has vids are actually dope and he actually explains shit ;)

also, there's erigitic who's dope aswell

Also, instead of just copying code, try changing it up, and try fully understanding each line and what it does. If you're having trouble understanding something or are stuck with a bug, use google/ask on the facepunch gmod forums (just not dumb questions)

Good luck :)

You can check this out for a basic introduction (if you have some programming experience already it'll seem repetitive to you), there's just one video at the moment but I'm making more