It is hard to say without seeing your adult websites and ads you are running on them, but poor conversion rates are most of the time are the result of the untargeted traffic or unrelated ads. You should first try to promote offers that are related to your niche, so if you have a video tube with webcam videos, then sign up with live sponsors and try to push them on that site and see what happens.

Another reason why you do not have any conversions might because your traffic is untargeted which kind of relate to what you are advertising. If you get some organic visits from Google for the keywords of “busty teens” and you promote something totally unrelated to that niche, then your conversion rate will be very low.

Did you try monetizing your websites with cams? Try to promote MyFreeCams through Crak or Chaturbate for some time on the revshare payout and see if you get any good results.