People would bring goods and to a river to trade
The Caravans that came to trade brought gold
Once the people layed out their items to sale they would bang a drum to let the other people know the items to trade were ready
BONGGG
When the other people came to trade they would leave gold for the items
BONGG
Once the people came back they checked if the other people left enough gold and if they didn't they would leave the gold for more
Once the other people came back, they added more gold if they needed and they would do the same process again. If they left enough gold they would take the items and leave