In power fantasy mode, you can get treasure by asking to Kobolds to go out an get some. You can do this in dark fantasy too, but that costs morale then, which can only be replaced by treasure or women.
There are a couple methods for getting treasure involving Mina. If she is happy, you can ask for 1 treasure from her as a form of rent. Additionally, there is a quest from her where you steal treasure from the Mercenaries. Finally, the Kobolds can find a dress that can be used as 1 treasure, or given to Mina to improve her mood.