Here are some affordable options for prom. If you are US. based, don't be afraid to order from the UK, they offer some great (and cheap!) options. Just order way ahead of time, know the return policy and ALWAYS have a back up plan.
LOVE the touches of cobalt blue! They would be great to brighten up the fall and winter. All of these pieces don't necessarily work together, but they all WORK! (Although there are some great mix & match options here) Any of these seperates would add a lot of fun and a lot of funk to any wardrobe!