When I started out doing craft fairs many moons ago, I covered a large cork board or a foam core board (buy from Michael's) with a solid white sheet. Just pull it tightly and use a heavy duty stapler to staple it on. You could also use black or another solid color sheet that your jewelry looks good on. Hancock or Joann's often has fabric on sale. Take your jewelry to the fabric store and see what color it looks best on and "jumps" out at you from. Use long straight pins to display your pieces on the board.
Of course, wearing your jewelry is always a great way to promote yourself. Also, be sure to remember not to take any criticsm personally. There is always someone out there who has to be critical. Besides being a creative person, you need to put on your business hat and promote your jewelry. What make its unique, what materials did you use, is it hypoallergenic, you might even give your pieces names (like an artist does). If you are serious about making this new hobby a business, you might want to consider buying your findings from a wholesaler. I use to use Rings and Things (http://www.rings-things.com/). You may need a business license.
Best wishes to you in your new creative endeavor. Let us know how it goes.