There is no reason the economic system in a fantasy world would have to be significantly different from the real world. First you have to decide on a stage of development for the economy in question. Is it a primitive economy based largely on barter? It is a pre-coinage society where wealth is transferred in something like salt or hack silver or seashells? Or is it a more modern economy with official coinage? This gives you an idea of what is valued. A medium of exchange needs to be rare enough that it has value, but common enough that there will be some to change hands on a regular basis. Maybe you even have a fiat currency, backed by little more than the perception of wealth and power, which would cause that perception to be aggressively defended.
You also need to think about credit. Without credit, you have a wealthy class that holds most of the wealth and therefore owns everything. With credit, you can start to open up a middle class that can get the money they need to open up shop without the backing of family wealth.
So, if you want a comprehensive approach to economics in a fantasy world, one place to begin might be with classification of different levels of economic development, different monetary systems, and different systems of credit.