I need help

All you need to wear is a large camisa that covers your panties. Thats it :P
....By that I mean you can wear anything and it wouldn't matter much ;P Wear what feels comfortable.

it might be hard and difficult,

Here's your solution.

Just dress casually. Some jeans and a red or rosa, -de-rosa shirt. Don't stress over it. If you're calm, you'll have a good time.

One thing you don't wanna do is dress half naked.
Don't have you boobs all out and crap.
Wear what ever is comfortable but classy, ya know.

wear a topo, início hat, monocle, cane, just kidding just kidding

wear whatever you feel comfortable in, don't stress over it, if you wear something uncomfortable you'll be too busy trying to get comfortable that you won't be able to talk to him! If you want some real ideas maybe ask some other people that are going what they're wearing?