Ask HN: How to promote social startup?

Hi guys, let me make a little intro: we're making a dream contest platform - www.dreamise.com This is a public wishilst where all dreams have a rating, every month we realize top rated dreams. Anyone can post their own wishes, get votes and boos rating and receive what he/she want.

So the main question is what are the best ways to attract users to this kind of startup and how to promote it?