@hamsou73 Sorry, but I won't tell that, as I did once and regretted it when the user in question copied my banner and tried to steal my spot so to speak, I vanquished him by creating an even better banner, that drained the referrals he would have got, so it was not worth for him to advertise their anymore. That incident made me really careful of what I say.
However, if you search a little, I think you can find a good spot very easily. And I can give you one tip, you just need to remember one thing, when you buy advertisement, go for the best deal you can go for, usually by getting the biggest packs as they cost less (for example 1day banner cost 5$, 1 week cost only 25$...). As I noticed that usually, the little packs are not worth it, you can buy one just to test, but after, you need to go for the big packs.
Also, I can talk to you about AdHitz (created by Clixsense owner if I am right), which offer good banner advertising in many different PTCs. You just need to find the right sites, but their spots are usually quickly full.
Edit : and thanks all people for the kind messages, nearly forgot to say it