Sounds normal to me, but I have never done much to backlink or research keywords. I suggest you visit the link at the bottom of the page that says learning center, or just go to http://hubpages.com/learningcenter/contents and find that big green button that says "earning money".
There are also a number of videos there like these
Increase AdSense Earnings With Placement Ads
A video guide to understanding the stats on hubpages to help increase your adsense earnings
How to increase your Adsense Earnings
5 Surefire Ways to Increase Google Adsense Earnings