Addons won't work properly.

[Gadgetguy]

I bought Garry's Mod, but I only have TF2 as a Source game.
My friend and I have installed the same addons but some of mine don't work (Minecraft Swep, Halo Swep, Nuclear Warfare 4)
The only difference is that he has Half Life 2 Episode: 1 + 2
Would they work properly if I bought Half Life 2?
What base do most addons need?

Thanks for all your help

[RobiePAX]

It's hard to tell. Half-Life 2 is definitely a core game. Many todays custom maps, game modes, addons and materials require CS:S.

But you should double check that you installed an addon properly first. If after you installed an addon it doesn't appear at GMOD Main Menu - Extensions then you installed it incorrectly.