What to wear for David Guetta concert?

Im going to see David Guetta at the O2 arena end of this month, I haven't a clue what to wear?? I saw him at creamfields last year but everyone there just wears wellies n muddy clothes! I dont wanna look a tramp but not too dressed uo either...Any ideas? and I aren't rocking out in my birthday suit either before any of you suggest that lol