If this helps.
I have real content sites, well established long before AdSense was even invented.
I have NOT substantially updated these sites within two years of the advent of AdSense.
Twelve years later, for whatever reason, my sites are now going gang-busters on Google [read better than years before - if that was possible]. Remember nothing has changed except possibly being turned up another notch as "authoritative" sites.
The only sensible answer I can give to the original poster and others is:
"Devote yourself to producing good quality unique content. Forget AdSense, build good unique sites with content people want to find".
I have $100,000's+ of income to dispute that theory.
Don't take shortcuts.
Admittedly I'm speaking of 12 years ago which in internet terms is a few light years of difference.
You want to succeed? Write up a 5 year plan, forget AdSense, forget all else [why does this seem to me like I'm talking to my older teenage grand-sons?]
Anyone can succeed on the internet.
Anyone can succeed with AdSense.
BUT "not" with a site you established last week with AdSense in mind.
FWIW: I recollect back in the early days of the Amazon Board [before AdSense for purists] when a genuine lady asked:
"My car is due to be repossessed, how can I earn $1,500 with the Amazon programme by tomorrow".
True story. Ah! Why I be cynical?
Riches simply don't fall out of the trees.