i agree with the going to vet part- they will know what the cat will need.
As for cat or kitten- go to the shelter... if you have an idea of what you want then great, if not...look at the cats there- we went to the shelter looking for a black male kitten and came out with a tabby female...she was too adorable and is perfect for us.
if you have more then one shelter around you visit them all...or untill you find yur kitty
good luck!