Witchling's Revised Guide to Making Treasure:
1. Play the games. There may only be two of them right now, but both of them can earn you a decent amount of treasure.
2. If your dragons have Familiars, BOND WITH THEM. This gets you free treasure and/or items every day.
3. Collect your free item from Pinkerton's Plunder Pile (Shop > Trading Post > Pinkerton's Plunder Pile) every day. If it's something that you don't need or don't want, sell it.
3. Complete Crim's quests. More quests are added every hour, on the hour. (Shop > Trading Post > Crim's Collection Cart)
4. If you have the necessary items, trade them out at Swipp's for rarer items! (Shop > Trading Post > Swipp's Swap Stand)
5. Sell any food that your dragons don't eat, materials, or battle items you don't want.
6. If you know you can get more than the selling price for an item (found by hovering over an item in your hoard), sell it in the Auction House (Shop > Auction House)! As of 11:48 AM Res time on 6/19/13, I have made 1,993 treasure off of selling my extra items in the auctions.
9. Breed your dragons! Dragons are able to be auctioned.
10. Gather items! For the first day or so I'd gather the food items that your dragons eat. Since you can get food items by fighting monsters in the Coliseum, I wouldn't really worry about it after that. After the first day or so, gather items by Digging and Scavenging! You can get items that can be sold for a lot more than the food items.
11. You can find dragon eggs! Dragon eggs can be found through the Coliseum and through Scavenging. They can be either hatched or sold for treasure!
~ This is all I have for now, but more will be added if discovered. ~