Girls won't be wearing dresses as it's more casual but I was thinking black jeans, I just need ideas on a nice top which is quite dressy and shoes, thank you x

Black jeans are something you can wear for every occasion, you can never go wrong with them - they fit everything. But since this is a party, maybe you should try dressing it up a little bit with a more festive shirt, preferably bright-colored (your pants are dark and you don't want it to seem like you didn't try ), add a blazer and some heels, let your hair loose and voila ~ Enjoy the party!^^

I would say a nice top could be: or any other tank top like that. If you wear a dark colored tank top, black would look good, but maybe brighter color jeans would be better. Wear some heels or wedges.

How about a cool black bodysuit?

with BOTH IN WHITE

yes.