Ok, here is my 2 cents, first your site is nothing special, I don't mean it in a rude or offending way. Its just that there are millions of other porn sites out there that you are competing with and you have to do something a little bit different to the norm to make some cash.
Unfortunately with your site the way it is, I suspect that no matter what traffic you purchased, regardless of niche it would generate very few signups.
You need to think outside the square and offer something that others don't.
For instance there are probably millions of surfers out there that just loves grannies in panties, now I have never seen a grannies in panties site and I have no intrest in it, but there are some surfers that do and if you can find them and direct them to your niche then they will buy.
For instance if I brought 10,000 panties uniques & 10,000 grannies uniques and I directed them to my tgp / mgp site
www.granniesinpanties.com (url is even for sale on sedo for $300, or you could register the .net version) which only had grannies in panties content then I would suspect that I would make a small profit from my 20,000 surfers.
Find a niche that is not saturated, setup a site, add some sponser galleries, buy some targeted traffic and watch the sales roll in.
Making money in adult is not rocket science...