To create your own jewelry line, you must design items and find a company to either supply you with materials to make the items or manufacture them for you.
To have your own jewelry line, you first need the funds to purchase enough supplies to create enough jewelry to satisfy the demand. You also need a place to sell.
Speaking from 20 years experience, jewelry design is extremely competitive in the best economy. Look for good deals on supplies and make sure your customers know your work is unique.