you can add more new contents to get free traffic. when people love to read your contents, and then more clicks you will get.
adsense loves organic and targeted traffic. because of this you must get traffic from search engines and i suggest you to make seo
The best way is to put original content and update often. It will take time but your traffic will build as people become interested in your site. Also work on quality back links to related sites that can attract people to your site. The more you advertise, the more visitors you get. As your traffic increase, your money will increase.
I can't imagine a better way than search engines. It's free, targeted traffic -- which is by far the best kind of traffic.
Build your pages so that search engines love them -- page titles that contain your keywords, content that contains your keywords in every paragraph, content titles and subtitles that contain your keywords, image ALT tags that contain your keywords, META describption tag that contains your keywords, and page links that contain your keywords.
Agree with @allout.Just create good and original content and you will have big smile after that.GUARANTEE!!
Search Engine Optimistation => SE Traffic => adsens clicks.. love Google and unique content which I built!