Small braless breasts are very attractive. You don't need to hide your nipples.
Dress as you like,but you asked so halter top No bra and a pair of short shorts.
Shorts and halter top NO BRA.
I'd suggest you to wear one of these... as it covers most of the clothes by top designers...
Mmmm if you're okay with people staring at your nipples do you girl~ lol i'd suggest wearing one of those sticky bras that just stick on top of your breasts or if you want to go even more minimalistic try pasties? to cover your nipples... Or if you don't want to deal with it at all maybe just wear the dress with a normal bra. All up to you though, your fashion freedom of expression, dress for yourself and not others.