I bought 3 120mm fans (Akasa apache Black) for my haf 912 two for the top and one for the side, I looked and there is only enough pins for one more fan, do I need do buy some kind of adapter?
Get a fan controller, although you are probably best to get a controller that allows for 4 pin fans as thats what the akasa fans are and wont fit without modification on 3 pin ones
Watch the lost cost ones, some are made pretty cheaply, as a result they are often crap, only powering max of one fan per channel, I've found with fan controllers you get what you pay for.
If it was my rig, I'd have all the case fans connected to the fan controller.
Ideally you want one that can output about 20w's per channel, so you can group ya fans together, so ya top rear fans on one channel, ya front fans on one channel, etc etc.