Um, for an asymmetrical spinnaker you just need a halyard at the top of the mast (so, yes, a block or sheave).
For a symmetrical spinnaker you will also need a topping lift to hold up the spin pole (so, another block a bit above the spreaders). The pole also needs a way to attach to the mast so a track with an adjustable eye or is advisable. There is of course the pole itself.
I suggest that you find another similar size boat that does fly a spin and have a look at the hardware they use before adding stuff to your mast.
Good luck.