I was finding trade with Natives a little confusing sometimes, so I had a look to see how it worked. If you do it right, there is a lot of gold to be made, especially on the larger maps.
Native Gold
Native tribes have a certain amount of gold for trading (Available Gold) when you meet them, but this is not all they have and the amount increases over time.
The starting amount of Available Gold is based on the size of the tribe at the beginning of the game. 200 gold for each village and for each pop. e.g. a tribe with two villages of pop 1 and one pop 3 would have 200 x (3 (villages) + 5 (pop)) = 1600 gold.
The Available Gold stays the same until they meet a European. After that it goes up by 1/10 of the initial value every turn. So the tribe above would get 160 more gold every turn.
It keeps going up like this until it gets to a certain value (Total Gold) determined by the map size, the difficulty level, the game speed and the tribe.
