Re: I don't know where to start.
You can ignore Lua modding for now, that's for more advanced scripting things, reprogramming the game basically.
If you want to get started, grab a mod from the
Minor Mod Dump here and play around with it. Tweak it, overpower it, underpower it, do whatever you like, and just get used to how variables have to be properly capitalized, tabbed, and numbers within tolerances.
When you feel comfortable, add on, make a copy of some weapon in the mod and play around. Eventually, strike out on your own and make something entirely new out of your knowledge. Even if it doesn't work, don't despair, just figure out what went wrong (or ask one of us) and some time in the future you'll find you can mod fluently.