Kinda looks like Pocahantas
In the short run lighters, food, water, meds, coffee, candles, etc., will be good bartering items. But gold never loses value due to it's intrinsic value (its peculiar physical properties).
The brain runs on glucose and/or fat (if in ketosis) Fat (ketone bodies [betahydoxybuterate]) is more efficient, and burns cleaner, leaving behind less oxigen-reactive species. The brain requires a little glucose, but the body can make its own for that in the absence of glucose. The brain can also make its own insulin. Doesn't rely completely on the pancreas.