At some point the story line you unlock a retainer. The retainer allows for you sell things on the Market (Auction House). It's around level 20, about the same time you get a mount liscense. I haven't be able to log in enough to reach that point, so hopefully my information is accurate enough to point you in the right direction. If XIV follows in the foot steps of XI (which so far it has) there is no "trash" in the game. Everything has a use and therefore a value. Even used armor (@100% spiritbond) can be dismantled into Materia and placed in current armor.

Edit: The retainer is like a bank as well. I have been told it has more bag space then our toons carry on the go.