The Nacra 5.5 Sloop is a great boat -as is- and will give you a great fast ride. I used to sail mine solo without jib and then with another adult male my size, 190lbs. x 2, it has a wide range of useability. It is a great boat in high wind too.

Once you get comfortable with it, if you want to add a spinnaker, that will take you to the "next level" of cat sailing. But you don't need a spinnaker to have a good time on it as is. Adding a spinnaker will cost you money of course, ($1,000?) and add complexity and rigging time. If you can find someone who has spinnaker experience that will show you how to rig it properly, and sail it with you a few times, that will help a lot. If you have a place where you can leave it mast up, spin. pole mounted, etc. that will save you time and make it much quicker to get out on the water.

If you are going to race it in the Open Portsmouth class, forget the spinnaker for now, unless you are doing a long distance race with a downwind leg.