Try spending a week adding every domain name you see in ads placed on your site to the competitive ad filter. I had favorable results when I tried that awhile ago, but I'm not sure if it was a fluke or not.
You cannot earn a lot every click.. it is mostly by luck that you get a very good cpc... I get $0.01 for every click many a time but this is not that bad... 42 clicks for $2 means almost $0.05 per click which is a very good cpc.. try to increase the clicks by promoting the site instead of trying anything else