I have just finished up a jewellers apprenticeship here in British Columbia, Canada and am amazed at the work you are doing. I'm the same age as you and am going to school next year for 3 years to refine my skills. I've been spending lots of time learning zbrush and trying to see ways it can be used in jewellery. It's so nice to see what i've planned actually working in a practical sense! A big help you may find is a program called Gemvision Matrix. You can build basic - intermediate rings within it and it has all the presets for different gems and settings. As an added bonus it's based on rhino and exports to STL, so the possibilities between making settings for stones in that, and modelling in ZBrush are ENDLESS! Keep posting! I really like seeing what you're doing