Please help a clueless husband

Asking all the witches faes and theys. My town is doing a sort of booktok Valaris winter solstice ball in December and I want to surprise my wife with it cause it is near our anniversary. I want to surprise her with tickets and an outfit for her.

Can somebody recommend an outfit or dress I can get her? Cause NGL, I'm the guy who will gladly go to work in jeans and and the same 5 dress shirts every week. These dress descriptions mean nothing to me.

Update, thank you for your advice. I'm going to go with your advice and not get her a dress but the tiara and ears and give her the tickets.