The economy in the plugin forms a closed system. The Settlers produce goods they consume or sell. There is a global market, which will be fed from the settlements offered. However, this requires that the settlements produce a surplus, which they then sell.

There are some goods that can not be manufactured by simple settlements, but which are necessary for the development of a settlement. Doors, boxes, signs, etc.

Therefore, it is important that the Admin expand a settlement that produces these goods and sold. As long as the automatic development of settlements is not enabled players or admins must help the settlements. My tip: Extending The first settlement as far as possible.

It is also necessary a settlement with enough money so equip the player can also sell their goods. The trade comes about only when several settlements are present. These should be located in different biomes.

The settlements and NPC use money to buy and sell items. You can call it what ever you want. In my imagine this is a silvercoin. But important is the relation of money to basic consumption items, the price of food.

1 money = 3 food (WHEAT) = 0,33 money/item

Each NPC need 1 food per day to do not starve. This make him not happy only make him full.

The money are produced by the settlements. There for they give Valuables (GOLD, EMERALD, DIAMOND) to the bank and get money (coins). That is the reason the settlement is very happy when you give them valuables. Valuables can not be produced, they must be found in the world. When the money is low in a settlement, the manager get some valuables from the warehouse and give then to the bank and get money for them. Because Minecraft has no coins the money is only virtually existing.

Like any good trader the npc buy cheap and sell expensive. The prices not very from settlement to settlement. This feature is too complex and requires additional cost and price calculation. Also it requires a local or individual pricelist for every settlement.