I would always put a link to a hub from the last gallery of your free site. IMO it's best to ignore pagerank entirely. Yep, entirely. Think instead about having your free site on GreenGuys Mature page, ranking #1 or so for "Mature Women" on the SE.. that spider is very active on his page, and now that YOUR site is listed on his page, that spider will spider YOUR site, and follow your link to your hub (is it a mature oriented hub? even better for you!)
But thats my opinion
Test things for yourself, see what works for you.
tgp's a waste of bandwidth? Not sure I understand the question.. Do you mean to ask if submitting galleries to tgp's is a waste of bandwidth? I'd say no. For the exact reasons above, the real use of tgp's to your galleries is getting traffic to your sites and also hopefully to your sponsors of course
Is running a tgp a waste of bandwidth? Again I say no. A text tgp with well coded pages wont burn alot of bandwith by itself compared to building galleries (for instance). And again, depending on your linking, you're after search engine/pre-targetted traffic. So it's possible to burn very little BW and get good rankings with some hard work and experimentation.
Anywho, test test test test! It's hard work, but it's good to try everything you can think of
Good luck!