I'm an Adsense publisher since 2006 or so.
I have quite a few websites and I have managed a lot in these 10 years.
Over these years Google Adsense was something like 90% of my income.
What kind of your website perform well with adsense? How about classified ads website do you try before?
Conversion and earnings varies a lot dependent on what the website is about.
I learned that websites about stuff that people wants to buy tend to perform a lot better than, for example, websites with funny videos or funny pictures or even informative websites like wikis.
And stay away from anything tech related.
I never did classifieds, too much competition.