Prom dress alterations???

Je

So I bought this dress a while back for £10 and although it looks beautiful its let down by some of the parts of it. The cups are just two cheap pieces of foam that are visible and move around and the bottom half rises up so everyone can see your business😕.

One of my friends never to have a prom ( neither did I ) and their are throwing a last minute prom at their house! I cannot afford or even want to splash out to buy a proper prom dress like the other girls will have but who cares! I’m gonna re design this beautiful thing.

My dressmaker is putting new cups and making it a halter neck that you tie at the back but my main problem is the bottom half. Idk what to do with it! The underskirt is so cheap and rides up like crazy so it has to go vut something needs to go under the fabric. Any suggestions???