Steelseries makes very good mice. Many of their mice are priced very reasonably too. I'll buy the kinzu or the xai as my next gaming mouse. Also, my current mouse is the Logitech G9. It's okay, and the tracking is defiantly quite good. I have fairly large hands though, so I would prefer something a bit larger, particularly beneath the palm. Really, there is no right answer to your question. Go to a store that sells gaming mice, if you can, and try to get your hands on as many mice as possible, to see what shape you prefer.
Here are a couple of articles comparing mice: http://www.tomsguide.com/us/gaming-mouse-performance,review-1472.html
I currently have 191 games on my account, plus about a dozen more that I bought as gift passes for and haven't yet given away. The complete list is here: http://steamcommunity.com/id/tricelit
As far as what I'd recommend the most, you can't go wrong with all of the Valve games. Grab the Valve Complete pack, it's the cheapest way to catch up on a ton of classics (plus it's on sale 'till Monday). My personal favorite Valve games are the Left4deads, Portal, and the Half-Life 2 games, particularly Episode 2.
To pick a cheaper game, I loveWorld of Goo. Grab the demo and see if you do too.
If you see Mirror's Edge go on sale again, I'd suggest you pick that up. There are a couple of frustrating spots at the end, but most of that game is a complete joy.