Like I said in the other topic just yesterday, I rarely do media buying these days, for many reasons, the main one that I always had more success getting ranked on search engines and I find it more profitable.
However, when I buy and sell traffic I am using PlugRush and JuicyAds. But I have to warn you that if you have not done that before, you might lose money before you see anything, because it requires a lot of optimization, testing et cetera. It is not like you will spend $100 on the first campaign and you will make $200 back unless you are extremely lucky.
The rates are pretty much similar on all these ad networks, but Juicy seems to be paying more ad spots, at least in my case.
IF you have a tube, then you might find promoting adult cams like Chaturbate or using smart links from CrakRevenue way more profitable. I can not tell this, since I do not know your site and your traffic, but you should try different things for sure.