Macbook storage space and mouse opinions

Hey guys I have a Macbook (the one where the volume keys are on f3 f4 and f5). First I need to know how much storage is memory on it, and if I should get an external hardrive for it or not if I play steam. Lastly, would you guys prefer a tactx mouse for 50$ over a Rat 5 for 70$ (I am only willing to spend 100$ on all this computer stuff, including getting lion, a mouse, and a keyboard)? Thanks for the help!

Hey I got tactx and figured out how to check my computer's hardrive space, thanks for the help guys!