One way to set yourself apart is to focus on a particular type of jewelry. I know people who make a living selling only earrings, while others do exceptionally well focusing on anklets. If you want to focus on one type, choose something you are most comfortable with and become an expert on it.
You can also set yourself apart with a specific technique. Chainmail or precious metal clay are two good examples of a technique of jewelry that you can specialize in. You can do very well if you become known as the go-to person for a specific type.