Best banner ads provider in terms of ECPM

[Justify23]

I'm a new developer and wanted to get more ideas on how to earn from making simple apps. For now I have 2 apps in the apps store and I only placed banners so the users won't be annoyed with so many ads. Currently I've used Admob(which I got a 1 month ban), StartApp(which only gives me 1cent for 400 impressions and currently I'm trying Facebook. Anyone has some idea on what other ads provider should I try?