Bars/pubs are very casual. Dressing up will make you look out if place. Clubs on the other hand are the opposite end of the spectrum. Its all about looking sexy/slutty and showing lots of skin while making it look likfnyoure still trying to be just a bit classy.
A chicken suit,I get the most attention if I am wearing it
What ever you're comfortable in. Many bars have a dress code, so if you're going somewhere specific, find out what the dress code is. It might be something like no jeans, no trainers, no hoodies, or whatever.