Best Banner Ads for My Site

I am having issues deciding which ads would be best for the banner locations on my site. A few details on my site. It is a GameCube oriented site, thus most of the people visiting it are younger and do not have credit cards. Therefore, my current ads are not working. While they are for a free trial, you still need to put in your credit card information. So I am getting few clicks and even fewer actual signups. What would you guys recommend I place on my site to get the most money?
Thanks, darkNiGHTS

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