What should i wear to a fancy italian restaurant?

I'm 12, and my cousin is graduating high school. obviously he's a senior. i have to go to a fancy italian restaurant to celebrate, along with my extended family. my mom said she wouldn't buy me anything new, so i'd have to just deal with what i have. i have a dress from abercrombie, but i feel like it isn't fancy enough. i was thinking of wearing a black ruffle tank top tucked into a floral pencil skirt with pinkish-skin tone heels. would that be appropriate? oh and i wear make-up by the way. oh! and what would be a cute hairstyle? i might put it up. either that or i'm thinking of curling it.