It is notoriously difficult to get people onboard on marketplaces (see http://news.ycombinator.com/item?id=2898589). By asking people to pay a subscription, you are making it even more difficult!

I don't know what you're testing with this fake landing page. There is clearly a need for marketplaces as Craigslist, Ebay, Airbnb, Etsy etc have shown. It's just difficult to execute.

You need to be clear if you want to build a marketplace or not. If the answer is yes, then you need to build something small but useful and figure out a way to get users.

You will have the luxury to solve the spam problem once you have any traction at all.