First problem was the coins. To buy something the dwarves had to haul the coins to the seller, one at a time of course. And then when given change they had to haul the change back to their room. One at a time. And the merchant had to haul their new coins, one at a time, to their room. But that was an easy problem compared to the real difficulty.
The other problem was balancing incomes with expenses. Everything was just assigned arbitrary numbers, and those numbers were fixed. So in one player’s fort they were building a huge mega construction out of glass blocks and so the glassmakers become wealthy beyond the dreams of avarice simply because so many glass blocks needed to be created. But the weaponsmith was only ever asked to create ten battleaxes for the single squad of military dwarves so he went broke. After all, everyone had to rent a room and eat. Prices need to depend on scarcity and the need to eat as much as on the labor needed to create an individual item. The weaponsmith might have earned more income for a sword than the glassmaker did for a glass block, but that didn’t help him in the long run.
The main goal is PoE or PvP, but actually I ended up fully playing for the economy.
You can get a job with its own leveling system, like a farmer, cutting crops, collaborate with a baker who will make you a cut so that he can get baker xp, and then sell the bread in an auction based local marketplace for player to buy and heal.
You can as well just arbitrage: buy something cheaper in one town, and sell it in an another where it was more popular.
I ended up with a tone of paper notes, just calculating the margin of different product, e.g jewellery, so that I can buy the materials, calculating the risk of loss during the building process, partner with someone for some materials, and then finding where to sell the end product