Personally, I LOVE a well dressed/groomed guy. It's such a turn on, and my friends all agree. An average looking guy can be hot just in the way he dresses, and vice versa, a hot guy can be a big turn off if he doesn't dress well or has bad hygiene. Good shoes, nice jeans, and a casual button down shirt is gorgeous.
If a guy was nice and I liked his personality but he dressed horrible, I would still like him. But dressing nicely will probably get you more attention from girla cause my they will notice you more. Personally, I think dressing like a greaser with a white tshirt, cuffed jeans, and sneakers is very attractive, but each girl has her preferance. Just dont sag your pants, im pretty sure no girls find that attractive.