Main Group for my friends and such.

Hi

I can't teach you better than the threads for SourceMod and TF2Items. However, I can help with installing/editing. (Plus, SourceMod allows other plugins, like a TFBot Weapon Randomizer.)

Zappy, may you teach me how it works?

You may want to note this: Editing items_game.txt changes values and such for the first map/stuff, but after a map change or anything (at least prior to SteamPipe), all values get reset to the default (even though no .txt or anything contains it, and items_game.txt doesn't get altered...).
I'd suggest using SourceMod and TF2Items to apply item attributes to the player "*" (that means everypony).
If you want, I can edit tf2items.weapons.txt for you, since I know how it works.
I just need to know what weapons should do what. (Note however, that item sets can't be edited this way.)