Now, of course, you can always buy jump rings. I buy them regularly because they are just handy to have around even though I can also make them myself. Another thing to consider, depending on what you are making, is that you can also purchase pre-soldered jump rings from many vendors. I like to use these as well, especially when Im making a necklace or bracelet. I can attach them to a bead tip
or secure them with a crimp bead
One place in particular that I recommend for jump rings is Urban Maille. They sell excellent quality rings, and they have some fabulous tutorials on their site, complete with illustrations. If you struggle with jump ring techniques, definitely take a look at their how-to section.
For more jump ring suppliers, check the list of vendors I have listed under Wholesale and Retail Jewelry Making Supplies.