Here is the trading Forum. It is a good place to find people who have the same Niche website as you
Traffic Trades/Gallery Requests - GoFuckYourself.com - Adult Webmaster Forum
As far as buying backlinks. I know they work. I see how my clients use their back links and I watch their progress. I also know that SEO is multifaceted and everyone has their own opinion. Email me if you need any more advice.
[email protected]