Even if games don't support it there are third-party programs like Xpadder and Joy2Key that would allow you to assign keys to the extra buttons on your mouse. Plus, a quality mouse is just nice to have, for gaming and otherwise. You can't really go wrong with something like the Logitech MX518.
I would say it depends upon the "Gaming Mouse". I find the Logitech mouse i'm using now to be quite sufficient with 3 buttons + the 2 extra on the side. After 5 buttons you really get into that weird area imho. As the saying goes Keep It Simple Stupid and with 5 buttons that is enough.
I don't really use any of the extra buttons on my Logitech MX518 for games, but I love the forward and back buttons on the side. It very weird trying to browse the internet with a standard mouse nowadays.
The MX518 is a really nice mouse too. Not very expensive either.
Great to hear, I always wanted more buttons on the mouse when I game(and I the closest I come to a FPS is Fallout). The mouse you guys all recommend was the one on my wishlist on Newegg, it was the highest rated, I will definitely get it. I use mouse navigation shortcuts with Firefox but I guess the forward/back buttons are even easier.
Right now I don't use a mouse pad, are they really needed? I have not used one in years.