That's a bit of a tough question because it will vary from one person to the next. Ultimately you'd want to look critically at what you're making and your technique. If you are confident that your jewelry is sturdy, well crimped/stitched/finished etc then I don't see why you shouldn't sell it.
If you're not sure or you're not entirely confident, you might try taking some of your pieces to a local bead store and have someone look them over for things that could be improved (and possibly show you correct technique), or perhaps post some pics here for constructive criticism. You might also look at what other people are doing either online or in stores, and look at the details that make/break a certain piece.
I would also reccommend looking at some books or online about how to price and where to sell. Doing your research will help you be more successful, but it's a learning process no matter what. Try the websites http://www.jewelry-marketing.com/ or http://www.home-jewelry-business-success-tips.com/index.html. Vicki Lareau's book "Marketing & Selling Your Handmade Jewelry" is also good.
Hope this helps a little!