Since you make $20 a week with blog posts and $7 a week with adsense, you actually make $3.85 a day. Simple, make 3 more sites for a total of $15.40 a day. Making a new blog isnt too hard, and most of your revenue is because of your blog posts (Which is easy content).
well, thats a good idea, im finding out some niche that brings organic traffic and good adsense revenue. thanks.