It looks like you are going to make living space in the attic?
If so, you need to find 22 1/2" insulation,preferably faced.something you can staple to the rafters(3 1/2" should do) Otherwise, a solid insulation board(which I used for my barn/home,which has a R7 per inch, it is called polyisocyanurate, and can be found through some suppliers and with that are value is by far the best I have used for the money.
Insulating the floor spaces can be done with blown insulation, 12-16 inches or more if you can, without too much undue run over, blown in is easy and efficient.
Venting is adequate, as you stated, you already have vents in the 32 foot ridge? That's plenty. Gable vents are not necessary, but if you want, go ahead and install,I don't see them as needed because you have enough with the others.
Hope this helps,