Most Helpful Girl
Since you not used to being fashionable I recommend something quite casual and easy to wear.
e.g. a casual shirt like this link link and a good pair of jeans that matches the shirt. As for the shoes, probably dress shoes link , loafers or sneakers that don't look like sneakers link . Some clubs have regulations on the shoes (and clothes) you can wear, so make sure you check up on that before you go.
Go for something dark, anything light stands out too much in a club.
But at the end of the day it is important to be yourself, don't wear something your uncomfortable in.