I need help

All Du need to wear is a large hemd, shirt that covers your panties. Thats it :P
....By that I mean Du 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 oder rosa shirt. Don't stress over it. If you're calm, you'll have a good time.

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

wear a oben, nach oben hat, monocle, cane, just kidding just kidding

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