The usual: clicks and impressions (which I check daily) to see if pages are receiving the expected traffic, be sure to keep an eye on your budget and the cost per clicks and you be just fine :)
Oh boy, wish I could move to the U.S. and have something near your actual income.
I'm on my thirthies, married with an almost over the minimum wage stuck web dev job on Brazil :/
10 Steps to Master Javascript within 15 Months | Is it possible? - WhatsDev: https://www.youtube.com/watch?v=7JVNjwilPMU