Need help with cosplay?

There's a convention that I'm going to in two weeks time, and, as usual, I leave my cosplay to the last minute. I have no time for sewing or buying off the internet. So, I would like to either buy some cheap clothes that work as cosplay, or morph one of my existing outfits into a cosplay.
I have a mint green (almost white) formal dress that I've only worn once and have been looking for an excuse to wear since, but can't think of any characters that would wear it. I also have a gothic lolita dress; I'd cosplay as Chii/Freya but I can't do the hair. I also have cat ears. I have almost shoulder length short brown hair (which I can dye), and am a girl. Any characters that come to mind?

P.S don't refer me to animecharactersdatabase.com