Adsense make you decent money if you choose the right niche. I have heard Finance and health pay the most for clicks.
I think it is about the niche and traffic, I got 10,000 hit in one day and made $15, if I get about 3000 I might make $4. And the image ads sometimes pays better and the niche.
once you've placed an adsense ads on your site, you need to have a regular website visitors to earn from it