I know I am a bit late in replying on this post but here is my penny in the jar.
A mouse mat-pad can be as important to an FPS gamer as a good 40+euro mouse. But to be honest, choosing a mouse mat is directly connected to your gaming style and your peripheral surface area.
There are 2 different surface types for mouse mats. Fabric and plastic.
Fabric, allows you to finely control the mouse pointer's accuracy. AKA ideal for snipers and in general for those that require static accurate type of mouse aiming. Very suited for FPS games.
Plastic is perfect for the faster paced gamer. If u are the aggressive type that likes to jump in enemy lines and take down opponents in close combat, plastic surface allows the mouse to slide faster and unhinged. Also very suited for RPG games.
Now as for the available surface area i mentioned, most above 15 euro mouse mats require a bigger surface area. So make sure to take measures as well, Mouse pad thickness is also very important. The thinner the mouse pad the better and less stressful (i found) to your wrist it will be.
As for a wrist rester, i am against those. My personal opinion is that you should arrange your desk and chair so that your full arm rests on the desk from the elbow to the wrist at a vertical angle from the edge of the desk. I can almost guarantee less stress on your wrists.