Well it fits two on the front, two on the top and one on the back. So you'll want the two on the front to be intake, the two one the top and the one on the back to be exhaust. I use Corsair Quiet Edition fans in my case but they're expensive when you buy a lot of them but they do look awesome. To be honest though, some cheap red LED ones to go with the one you get with your case would be fine. Or if you don't want a glowing red build then buy the colour of your choice or may just non-LED ones.
You'd get away with just buying 2 because you could use the one that comes with the case already on the front and then the other two you could put one of them on the back and one on the top.