Open ended questiom..lol. It all depends on what you want to do. Most guys go with 14/40 gearing for a little more speed. Front gears are cheap, for most uses I would say go with a steel rear instead of a trick Renthal alloy sprocket, just because they last longer, but they still look sweet. Stick with a real name brand, not a no-name chinese. Go with an o-ring chain. I've seen complete Primary Drive sets for about $50-$75.