Depends on what you’re selling. If you’re basing your entire store front on random gear you find, you’re going to notice you’re not selling a lot. If you really pay attention to the maps, you’ll see some areas have shit for resources, so collecting resources in one area and selling them in an area it’s scarce is basic economics. Selling fishes in an area with no real fishing holes, iron/silver in areas that have no mining nodes, even water in areas with no clean water. Also, certain crafted items sell well, such as bags. It takes grinding to get enough FP to get runes of holding, but if you craft decent bags, people will buy them.