Jumping off from some of the good advice above, a solid straight air pop first is key to any trick, not leading the spin with your head and shoulders aswell, but the way I find best to describe how you want to set your spin is to set it from your core, use that central joining point to power you, not starting from your upper or lower body alone, this way you're not turning your feet and your head playing catch up or vice versa, its a whole body movement.
As you do bigger spins on the same size jump you'll need some of the momentum from setting with your arms you're currently powering you spin with, but they can only give so much before you end up spinning in parts as you've found, but if you can get the pop and setting from your core for a 3 on this jump dialed in, its the same concept for everything else.
