it does matter what he wears. if you dress like a 45 year old math teacher, expect girls to overlook you. if I don't like a guy's style I probably wouldn't even give him a second look
Justin beiber dresses fine. he dresses like a guy in his early 20s should. if u don't like that style and prefer something more traditional, go for the preppy style. and not Abercrombie preppy, but old money preppy southern frat boy swag.
You should wear what you want the right girl will love you for you. But i do like a simple causal look nothing flashy but that just me. I like laid back look. Even tho once in a blue moon id like to dress abit up.
It kinda is a materialistic world and no matter how much any of us try to deny it, we're all still attracted to what a guy/girl wears. I'm more attracted to guys with a not too tight, not too loose t shirt and a pair of fitted jeans. Nice boots/shoes. Someone with good taste but doesn't flaunt it.
Jeans and a button up or flannel on a normal day, maybe a t shirt
Dress casual. What's really attractive to me is a casual plaid shirt with jeans. Just anything really. I don't understand these girls you talk about. I would never consider going out with a guy looking like trash. I mean if I dress good I expect to have a guy dresses just as Nicely as me. Just saying.