What To Wear?

I was invited to a relatively good friend’s quince. And I plan on going but what exactly is “appropriate” to wear? All my other good friends are in the court so they don’t have this issue. Should I wear a really formal dress? Or something nice but not up to prom or evening wear kind of dress? Or would a black skirt and very nice blouse work? Its in only a couple of weeks and I still have no idea!!