I want to add one more book to Polly's list:
'The Complete Metalsmith' by Tim McCreight [R&T#62-010 ;
http://shop.rings-things.com/cart/pc/Book-The-Complete-Metalsmith-An-illustrated-handbook-499p17185.htm ]
A couple of reason's
1] Of all jewelry, rings probably need to take the most abuse and so... must be durable
2] Traditional metalsmithing/jewelrysmithing methods remain the best for such durability
3] McCreight's book gives a great basic outlay of metalsmithing and jewelry making
4] There is a great little way to make Silver metal clay durable for rings or to develop copper and bronze rings. That is to make a light weight ring blank as an inner sleeve for the ring you are making - that way the milled silver you use will give you durability and if you are using metal that discolors human skin the silver makes a protective barrier. the Downside: You still need to learn basic metalsmithing to make a light weight ring blank