My advice from 5 years of running channels is that I would skip trying to monetize with ads, it is a big hassle, takes forever to get paid and you don't make nothing unless you have a ton of viewers daily. A couple of ads here and there that don't make you anything is just going to annoy your viewers and run them off.
Honestly, I would recommend you try instead to find a sponsor or something similar. You'll make more money faster that way.
If you want still want to go with ads, do as Baradanikto recommended and find a reliable third party ad server. There was at least one in the forums here offering services.
Best of luck!