Traffic Junky has all the best sites in that niche. I think you need to check your options and use the banners on the top sites there, not the RON. I used them in the past and PH was the best one for me. The best spot was PH - PC Footer Square - 300×250. Also you need many good banners, NOT just the ones from your network (you might need to get your own creatives approved from your AM though) as lesser banner churn out pretty quick. Best way is to hire a designer and come up with new banners every now and then. Also, if your banners suck from beginning, very low CTR is obvious. I quitted as I didn't want to continue with the niche due to personal reasons and so, I am giving away this info here from my tests which will defo save you time and money. Test it out yourself and buy me a beer someday