What do I wear to a alternative/rock/pop gig?

I'm 13, average/tall, slim female with dark hair. I'm planning to go to a gig this month but i'm not sure what to wear. I went to a gig of the same band a few months back and felt really out of place because I was just in a vest and jeans and all the girls there were glamour-girls (maxi dresses, heels etc) :L That said, it was a youth club place in Richmond full of rich kids. Anyway, this time i'm going to a sort of club/restaurant/bar place in Southampton. It seems quite stylish and trendy and y but I don't think i want to risk heels. Would my dark blue skinny tee, jeans and leather lace up pumps be ok? Heels or no heels? More dressy? Shorts & tights? Help would be much appreciated ,'D