Most Helpful Guy
doesn't matter what you're wearing, if you're attractive some buzzed or drunk "slob" will go for it.
Most Helpful Girl
Wear what you want to, just act like you don't see or hear guys when they come up to you. Slap their hand if they touch you. Yell at them if they start being nasty to you.
Accept free drinks (if you see it and know he didn't put anything in it) and then walk away.
Don't change your behaviour or the way you dress because guys don't know how to act, just use it to your advantage.