Outfit idea's please (:?

I'm going to two parties in a couple weeks time and I have nothing to wear. I'm saving up for a car so I don't have a lot to spend and I need two outfits as I can't wear one outfit on both day's as the same people are going to both. Anyone know of 2 fairly cheap hot dresses & shoes that will look amazing. In the UK please, either describe them or pictures would be fab.