Outfit for Prom/OOTD

Hey girls how are you? It's such a beautiful day outside and I'm counting the days till my vacation at the seaside! And just a couple of weeks before I go I wanted to show you an idea of an outfit for prom.
Here in Bulgaria when you have a prom you invite your whole family and your friends to a restaurant before you go to your school.And of course it's a formal occasion so everyone must be with formal clothes.The question is how to be beautiful and elegant but not more than the prom girl when you are invited to such a party?Here I have one simple idea for an outfit for this special occasion:

The dress is a MUST at the prom night and I think that if you are just a guest black colour is perfect for a dress.It shoud be long just above the knee.

For the shoes I chose these white shoes from H & M which were around 20$

I combined the whole look with this black and gold watch by Ungaro which was around 60$.
I can't tell you how much was the dress because it was a present for me but it's not more than 50$.

I hope you like the whole look and you choose something similar when you are a guest at a prom. :)