The BEST advice you can find about optimizing for Adsense comes right from Google themselves. They have page after page of advice, case studies and all that.
Thy also have a team that gives specific advice. I don't know how you get selected for that, but they contacted me last year and suggested some minor changes at my main site. Realize that they want to make money too!
Anyway, the changes didn't really help, probably because I've been doing Adsense a long time and have tried everything already and had long ago settled in to what seems to work best for me.
That doesn't make me an Adsense expert; it makes me a "Adsense on MY site" expert; the team might have been more useful and dramatic with someone else.
Honestly, I'd pay a lot more attention to what Google themselves has to say than anyone else.