If you have a good stockpile of supplies you can build this up over time instead of just trading it away. First, never make a straight food trade. If a hunter offers you a possum for some medical supplies, tell them to throw in the fur. If a woman offers you canned goods for reusable diapers, tell her to throw in a basket. Do your best to always be giving people new, replenishable resources such as meat, furs, and firewood in exchange for the more valuable processed industrial goods.
As long as you’re fair, consistent, and trus– worthy, a merchant can also make a decent living as middlemen. People are accustomed to going to a store, handing over money, and taking goods home. Even hardcore Ebay addicts aren’t used to the time and energy it takes to barter. A hunter could waste hours trying to haggle for the right price for meat, or they could let you do it in, exchange for a small cut. That frees up time for them to get out and hunt more meat. Everybody wins.