AdMob Tutorial Please

I'm trying to understand how admob works and easy/cheap ways to create apps to use with it, anyone has any tips?

Go with Reskin, you should find tutorials everywhere, integrate Admob inside the app and publish it, if the niche is in low competition you should start seeing earnings in Admob.
As easy as it sound, the hardest is to find the niche, and if you do you will bank Admob