How to get a mod started?

[Sabre]

As you probly already know, I've been learning to code so I can make my own games and mods. With the exception of pointers I seem to have a grasp of the basic, or at least enough to start playing in source.

However, I hit a problem. My original plan of 'Simply adding a buy menu' isn't as simple as I originally expected. So, I decided to start off easy by changing the weapons around. This is litterally a case of changing the numbers for clip size, fire rate ect. Hell, you can even do it by editing a txt file. (couldn't find where the carry capacity was kept though)

So, I need ideas I can use to cut my teeth on. Something easier then adding a shop or level up system, but harder then adding a weapon. Any ideas?