quick questions about painting my case

[furiousfords89]

i am going to autozone tonight to get some black (plasti-kote) spray paint for my case and i am wondering if i also need a can of primer and is primer absolutely necessary? Just for the time being i have decided just to paint my case's side panels and nothing else so will just getting 1 can of paint be enough?
thanks, and sorry if my questions sound n00bish