Depends on what you're comfortable in really. Anything you like will give you confidence so it's a personal style type of thing. Also, it depends on the type of club you're going to. But I honestly didn't know guys even think twice when going to the club lol pretty much jeans, t shirt, shoes and they go. That's what I usually see anyway. I can't even say I've noticed much what a guy is wearing unless it was a t shirt that said something kinda funny or interesting.
It's pretty simple for guys and if a girl is interested in you it definitely won't be because of what you're wearing unless she is into fashion like crazy.
As long as he looks relaxed in his clothes I like that, because he'll seem easier to talk with. Something clean, neutral colors, simple. I like dress shirts and slightly baggy jeans, I don't want to see you trying to hold your jeans up all night, trying to constantly adjust them if we're dancing.
If dude is at the club lookin' like a pimp, I'm going to have to pass.
If he looks like a crazy frat boy I'm not interest but I'll still think he'd be an awesome friend or someone to have lot of fun with!
I don't look at a guys clothes and decide to give a number or not. As long as he is dressed cleanly and in current styles, no biggy. I would not be attracted to a guy who was dressed over the top in any way, like too guido or too styled.
It is about your personality, if you act like the kind of guy I would date and if you act like a human being or are a jerk who appears to just want to score.
It's not what you wear, it's how you wear it. As long as you look manly and not like those typical douche-y/girly club-hopping guys, you'll be fine. Don't be a tool!