So to start you will notice that you need spoils to upgrade camps and also for 3 of the alliance challenges. But how can we get hold of these??
The answer is simple, for each action you take you have a % chance for the rare drop of the spoils. ie you put out a barter action then you have a chance to pick up a barter spoil.
Next question then, how high is your chance of picking up these spoils? Well when you have a camp at level 1, you have a 5% chance of picking these up, however, for each level your camp is upgraded you can add another 5%. ie a level 5 camp gives you a 25% chance of getting a spoil.
Camps can be upgraded to a max of level 20 giving you the 100% chance!!