Go with the classier of the two, even if you sweat a bit.
Actually, go with dark slacks and a button-down shirt (i.e. the type you'd wear under a suit). No T-shirt under it unless you have black body hair. Remember black socks, and suitable shoes (the shoes will impress her, it's a dancer thing).
Finally, be AGGRESSIVE. Maybe not cunt-punch, but just two shades under it. Rub a lot.
(why I'm helping you I have no idea)