Lighting is about letting the camera see what you want it to record. Before buying any lights try a simple exercise - take a table tennis ball, a golf ball, a tennis ball and any shiny sphere (christmas tree decoration?) and try shining ordinary lights at them. Use desklamps, slide projectors, maglight torches and soft lights like slide lightboxes. With a digital camera it is easy and inexpensive to explore which light suits each subject (and from which angle) and which does not. Then try the same exercise on other more complex objects with more than one surface texture. Doing this will teach you about creating the correct lighting for the camera to record which is often different from the best lighting for viewing. Once started you can progress on to transparent and shiny objects on different backgrounds.
What lights you need will be dictated by what you wish to photograph. A good inexpensive starting point is one good studio flash head with modelling lamp and small reflector, a translucent brolly and a silver Lastolite reflector.