Lowest Cost PPC Testing for Affiliates sites?

Hi,

I like to test PPC for my sites, since my site is new, I don't know the conversion rate of my site, so I do not know how to calculate whether is it profitble or not using PPC campaign. So I'd like to test PPC with the lowest cost possible.

Could you suggest what PPC should be used, that can provide good traffic at the lowest cost, so you can get the feel about conversion rate of my site?

Thanks.

goclick.com is very cheap.