nobody in adult uses PPC very much... even buying adult PPC traffic on teh googles is a major fucking pain since they prohibit you from bidding on any of the good keywords like twinks, young, girls, boys, bukkake, etc. and adult traffic generally isn't worth as much per click as mainstream so it's harder to turn a profit on it... not impossible tho, as there are some peeps out there making some money on it...
anyway, some of the best quality adult traffic seller out there is GTSADS they normally do large volumes, but they also have submit passes and such if you're starting out... really I'd only recommend GTS if you're serious and know what you're doing...
most other traffic sellers like trafficholder.com sell very low quality skim that might be ok for feeder traffic for a tube site, but don't expect to turn a profit from it...