If I did the fancy cocktails thing more often (read: ever), my dream team of dresses would include these lovelies:
Plastic Island Nightcap Dress, $150 @ Dear Fieldbinder.
Alice + Olivia usually seems more LA to me, but I think a New York gal could pull this off, with the addition of some black tights and a sweep of liquid eyeliner. Alice + Olivia Marcia One Shoulder Dress, $275 @ Shopbop.
A.L.C. Scarlett ruched lace mini dress, $395 @ Net-a-Porter.