Adsense does not tolerate paid traffic. You can generate traffic from search engines, directories, social bookmarking. Social book marking brings traffic to your website but when we have a adsense site, traffic from facebook and my space means nothing as it brings no clicks. Search engine traffic means more clicks and more revenue. Build and optimize your website for search engines. Without search engine traffic, there is no chance of making it big.
Never try to underestimate Search engine traffic. Search engine traffic is a traffic that is permanent as long as you focus on your website. If you have adsense only targetted traffic that comes from search engine that helps. Bookmarking and other services do help you in traffic but, they do not bring quality clicking..