Depends on what you want to use it for mr aumento. If you're the mmo-wow guy. A many button mouse might help you out tons. If it's for fps, buttons you don't need so many of, but more about adjustable weight and dpi.
I don't play either as main at the moment. So I've got a cheap 6 button "sharkoon fireglider". It's decent, fits my larger hands/claw grip. Not too heavy, not too light. I spend about 20 euro's which is like 15 pounds if not less. And I've been using it for about 2 years without a single problem.