You might want to develop a lens strategy to help what glass to purchase. Where you start depends on what you shoot, but many follow the strategy of buying the trinity [12 (14)-24mm f/2.8, 24-70mm f/2.8, and 70-200mm f/2.8)], which takes care of most anything you will want to shoot except for wildlife / birding, where you will probably want to add a 200-500mm f/5.6 before the trinity. If you are into macro photography, a 105mm f/2.8 will do the trick. You will probably want a 35mm f/1.8 and/or 50mm f/1.4 for indoor low light situations. If you are into astrophotography, probably a 24mm f/1.4 or f/1.8. That pretty much covers the waterfront except for specialty lenses.