Mods are radically different than making full games. A few new art assets, tweak the script, and boom you have a mod. It requires maybe a tenth of the effort that goes into making a game. This is coupled by the fact that people making mods play the mod so there is immediate gratification. And as Phemox states, for every 1 mod that gets made, there are maybe 100 that go up in vapor.

I think you would be best served by just making small games yourself. In 18 months you can build a nice portfolio for yourself and this will better equip you for school and eventual game making!