I think it's important to consider what kind of girls you are trying game.
If you are trying to game a standard colllege girl-pretty much any sort of generic frat guy stuff ( hollister, skate clothes, )will work
If you are going for a more classier girl-keep it simple. Plain tees are okay fitted jeans( that means not thuggishly baggy or emo tight) go for a darker wash of denim as that is a sign of quality, stylish shoes a must (puma,aldo,Tiger, steve madden, etc) Check out the guys on soap operas for an idea. Unless you skateboard DO NOT Wear Chunky Skate Shoes-girls don't think they are as cool as you do.
If you are trying to game a bohemian type of girl you can be a bit more creative. I usually go for this type. I get a good portion of my clothes at second hand stores( an i never fail to get compliment on my look) Just check magazines (details,GQ, Esquire) so you have good idea of what's stylish .your chances of finding somthing more unique then the generic department store affair are pretty good at these places.Not to mention it's usually more afforadable too. For a bohemian look think along the lines of how johnny depp dresses.
and all men shold own at least one cordaroy sports coat for the fall. It's casual and classy-perfect for college campuses and jsut bold enought to make you stand out from the rest of dudes walkin arround in hoodies.
Avoid childish novelty t-shirts with goofy punchline (pick up artishs, define girlfriend,vagina tease,Beer pong champion,stippers dig me, etc.) on them you didn't come up with. It exudes immaturity and lack of imagination.
Also avoid shirts with the name brand written explicitly all over it. No one cares that you spent 40 dollars on a t-shirt that a million other guys also have. Plus, who wants to be a walking billboard?