Trade in Skyrim is oversimplified and uninteresting. A particular type of merchant always has the same amount of gold and offers you the exact same prices as the same type of merchant in another part of the country. Merchants in small towns differ very little from those in the larger cities, and the only factors that affect price are your speech skill and any barter enchantments you might have.
If you've ever swapped one of your toys with a friend in return for one of their toys, you have bartered. Bartering is trading services or goods with another person when there is no money involved. This type of exchange was relied upon by early civilizations. There are even cultures within modern society who still rely on this type of exchange. Bartering has been around for a very long time, however, it's not necessarily something that an economy or society has relied solely on.
Identify your resources. What items do you have that you could easily part with? Use a critical eye to go through your home, and consider possessions you may have in storage or that another family member or friend is currently using. If you would prefer to offer services, honestly assess what you could provide for others that they would otherwise pay a professional to do. It could be a skill or a talent or hobby such as photography.