I'm going to a prom this upcoming saturday, and i need to get rid of my ashy/dry elbows and legs! how can i?

Hydrate!: Hydrate your self. Drink plenty of water. Also, you can make a "scrub" by mixing about a half cup of sugar with about 3/4 cups of olive oil. Put it in a jar and use it when you shower, gently rubbing the rough spots. After you get out of the shower, pat dry and while your skin is moist massage some cocoa butter on the dry areas.

Ashy dry elbows: If you see a dermatologist, they might do a mircrodermabrasion although that can induce post inflammatory hyperpigmentation (darkening) in patients with skin of color. Alpha hydroxy acids and retinoyls can belp.