For this one, I loved playing Dofus when I was younger. It was (hopefully still) a quite popular french turn-by-turn 2D MMORPG.

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