In the first phase, it will be almost pure barter.
Fuel, food, water, ammunition, lighters, alcohol, antibiotics (and other meds), soap, candles, and tools will be common value items. Services (labour, skills, prostitution,...) will obviously also be traded.
Luxury items such as toilet paper and trash bags will be in high demand.
People will try to use gold, silver, local currency and foreign currency as value items, but in case of a global collapse, that will be useless. All these thing only have value because people ascribe value to it. This will likely no longer be the case after a global collapse. While gold & silver are valuable in manufacturing, after the fall its value will not be obvious. Of course, there will always be hoarders which will buy up currency, silver & gold in the hope that it will be valuable again later.
In the second phase, communities will start creating their own currencies to ease bartering. The form of these currencies entirely depends on the options available to said community. Care must be taken not to pick something that is too easily replicated. Some will print their currency, some will mint it. Others will use formal IOUs or every day items validated or stamped in a particuliar way.
It is also possible that not communities but individual strong actors start using their own currency. Say someone who controls access to clean water. A group of people who took control of a goods distribution center. A gang of criminals taking control of an area forcing people to recognize their authority.
In a third phase, it is not unlikely that we will go back to a gold & silver backed currency. This might happen quickly around Fort Knox, but I doubt this will be in the same generation of people as the first two phases for your average community.