Gold, coffee, sugar, salt, medical supplies the ability to administer first aid, water purification supplies and or knowlegde. Batteries, tools , ammo, ...etc .all the survivor gurus will tell you, know where the local library is, especially with power outages. If you can read.
Nothing wrong with the barter system, if you have advanced knowlegde of how things will play out and what people will need, and just how fast, we become feral, with no food or water.