I'm sure I'm not the first person to discover this (and perhaps there's already a thread devoted to it), but as I was playing the Alchemist tonight with the City expansion, I learned how to have essentially unlimited gold.
In the City, go to either the Apothecary or the Magic Emporium. Buy either three potions from the Apothecary or three Scrolls from the Magic Emporium. This will cost you a total of 3 gold. But then you will have three magic items that you can alchemise for 3 gold each. Bam. Your 3 gold is now 9 gold. And if you have the Crooked Scales, it only costs you 2 gold to get 9 gold.
If you start with the standard 5 gold and then you go to the Apothecary first, you can go from 5 gold to 11 gold. Then you go to the Magic Emporium where you buy three scrolls (3 gold) and three Psychic Crystals (6 gold). You alchemize all of those, and suddenly you have 20 gold. That's good for all five warhorses from the Stables deck, which gives you a +20 bonus to your strength in battle. If you don't want to spend all of your gold in the first go-round, only buy four of the Warhorses. Then go through again so that you can get your Spell Book, Flail, and Full Plate. Two passes through the City, and the Alchemist is ready to go take down the Lord of Darkness and head straight to the Crown of Command.