With Deckathalons popping up I'm loosing gold like never before XD. I'll need to gain treasure cards much more efficiently now, and I need ones that vary in damage and magic school. For example, I'm a balance wizard and I'll be needing various Life, Death, Myth, Storm, and helpful non-balance damage treasure cards. What's the best way to rake them in (besides the library, my poor wizard is broke)?
I personally find it much easier to just buy Deckathalon TC from the Library. Don't need to wait up to 7 months holding onto TC and causing yourself inventory issues.
But if you want gold, Halfang in Wintertusk is one of the best ways to go. If your wizard isn't high enough of a level to get there, you could take up Fishing, or better yet, Gardening. Couch Potatoes are constantly praised for their amazing mega snacks but they are also a wonderful source of gold as well. They drop a different, auctionable snack on each of their harvests. In addition, they drop Empower, which sells really well in the Bazaar. Some of their TC are also good for Deckathalons! Empower was amazing in the Life Deckathalon because it let you finish the second fight on the 4th stage two turns more quickly, and Amplify also has a place in some battles.
As for other TC that you can get from Gardening, Evil Magma Peas (another plant good for mega snacks!) drops Pierce, which will be good when the Ice Deckathalon returns. Fish on a Vine drop 2-pip shark TC for Fire and Ice, which I personally haven't really liked on the 4th stage very much but they are wonderful on the other stages. Boiled Peanuts drop a 3-pip Kraken TC for Fire which will be absolutely incredible in the Ice Deckathalon. Fire Boom Shrooms drop Firezilla - lots of plants are good for the Ice Deckathalon now that I think about it. Silver Trumpet Vines drop Judgment TC, and while I have not been able to test how good Judgment will be (Balance Deckathalon hasn't happened yet), it could be worth checking out. Rotten and Dead Beets drop Deadly Minotaur, which can actually be used for a 2-turn kill strategy on the final floor of the 4th stage in the Life Deckathalon (Empower->Deadly Minotaur with the tier 4 Deck, gg).