Society is pretty limited with only resource gathering and consumption. Everybody is just scavenging for the basic resources and spending them or resting if they have enough.
To reach a more complex society, we need two main ingredients:
- specialization: instead of everybody doing everything, people can specialize and become experts in they field thus producing more
- trade: if expert in one field can exchange products with expert in another field they both have more of both than if they didn't specialize
First version of trade is barter where products are exchanged directly: one unit of food for one unit of stone, one axe for three units of wood. Problem with such arrangement is that both buyer and seller have to want each other's product or trade is not possible. As a seller, you need to find not only someone who wants your product but he have to have something you want (Coincidence of wants).
That's way money was invented: it is necessary. In money trade, as a seller you just need to find somebody who needs your product and has the money. Then you can use it later to buy what you need from person completely unrelated to the first trade. Naturally, I tried to implement it too. But to implement the money naturally, without some unknown force printing money and putting it into the economy (like state is doing now), definitely it's not an easy task.