We don't have to tell you to cut corners these days, but we still feel obligated to help you figure out how, so here:
There's a thrift store on the UES that's neither like Resurrection (too expensive) or Beacon's Closet (overrated) - The Arthritis Foundation Thrift Shop (121 East 77th Street). Yes, the name is weird, and yes, it resembles a grandparent's basement more than a shop that houses vintage DVF and Gucci (I also recently left there with a beaded Etro dress, with tags, for less than my Sunday brunch), but it's still where I go when I have a few extra bucks in my wallet and the spirit of adventure (you have to dig).
Plus? The store benefits arthritis, which means you can officially write off Chanel on your taxes - ok, not really, but go anyway.