Sell any thing you don't need. Sell any treasure cards you have many of an don't need. Play mini games several times an keep leveling up on the games. Diana Mythwhisper lvl 16
The simplest way would to buy crowns and exchange them for gold at Zeke, but if you can't, then try these tips:
1.) Play mini-games instead of catching air wisps, you heal while you play the game, and at the end you get mana and gold too, maybe a treasure card or two.
2.) Sell things you drop, like while I was saving for my house, I had one of everything: One hat, one robes, one shoes, one wand, etc. Also I sold all my furniture that wasn't a quest or picked-up item.
3.) Make a daily budget and stick to it. Example, you need some treasure cards but you're saving for a house, so your budget is 300 gold a day, so you buy 2 treasures that cost 150 each, and you don't buy anything for the rest of the day. Heck, you can make it 300 or something a week if you want! The key is to not urge yourself to flow over your budget. It's okay if it's, say, about 5 gold over the budget, but every gold counts.