the most efficient way to make gold is to....
1. do the daily chance everyday
2. get all your daily Gaia Cash everyday
3. play games (like zOMG!, jigsaw, tiles, word bump and dumpsterdive)
4. sell stuff you don't want on the marketplace
5. open a mini shop (for art, tekteks, ect)
6. do all quests that you can
7. take good care of your aquarium
8. save as much gold as possible
Welcome ^^ As for making gold, you have tons of options. The two that I usually use are posting in the forums, and playing a game called Booty Grab. Booty Grab will earn you, on average, anywhere from 1000-2500 gold per play.