Your ratio could be higher I think. The best way is to visit and look at galleries posted on differnent TGPs, learn what sponsors are used, how they are advertised etc...
Try different combinations of sponsors, links etc.
And yes, that's true that good content improves your ratio. It'a also true that you should tend to using text links instead of banners.
TGP traffic is hard to work with, because it's smart traffic.
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