Erm, just doing stuff in the site I guess. Posting in forums, doing polls, posting on profiles, browsing the site, playing games and stuff. If you want to know other ways just click your gold amount. It will bring you to a page that gives you tips and details on how to earn gold. :] Hope this helps. Your avatar looks awesome btw. =P
I use the site Dolphin Mania to play Gaia's Booty Grab game. It reduces lag and makes looking for a tank easier because you just have to look through the list of tanks and when you see the word "Play" click it and the game loads. You should try it out, it's the best Game on Gaia for making gold.