G-directory advertising is managed by AdBrite/BidVertiser. You can use AdBrite and BidVertiser to manage your ads, set CPC, see your ad views and easily pay for everything.
G-Directory AdBrite Listings | G-Directory.net BidVertiser Listings (Text Links)

If you want full page content for your games you can upload your Flash Game or Web Game Profile and then buy Premium Listings. This means your game profile will get more visitors. You can even offset the cost with Experience Points!