Dont use traffic exchange websites!! Just DON'T DO IT!
It's probably the worse idea ever. What are you winning? Nothing! The visitors from those are not engaged and they do this for the same reason as you ' they need more traffic'. And if you're going to work with an advertising network - they will ban you because of this type of traffic because guess what : it's not converting. Visitors from traffic exchange have a value of .01 -.05 per 1k visitors. Nothing more!
Instead, you can grow the website like everyone does and have success. There are a lot of tricks and you can learn a lot from google by searching terms like ' how to grow and adult website'.
I'm actually planning to write an article about growing an adult websites with a low budget in a week or so, I'll post it here too!
The best traffic source are search engine sites like Google. This kind of traffic is the best, but you may try tumblr and twitter as well, since they are porn friendly. I would add also reddit, which can bring some great traffic.
Also, check out the post from this website for this on traffic:
Right way is Best way. No shortcuts.
What ever is the topic of your site, always try to get traffic from Search Engines, Forums and guest posting by doing SEO, participating in online communities and sharing quality material.
It will generate traffic for long term that will prove to be more profitable. This is what I have learned while working online.
Traffic exchange will almost kill your website, Instead of it get some non watermarked pics and watermark with your web name and upload them to all possible image hosting,
share them with forums and see the traffic on yours.