PW:S is absolutely mandatory. I can’t take anyone seriously who says they don’t train it. Aside from being part of the usual soloing rotation due to kickback immunity, it’s also the best ‘Oh sh1t!’ non-talent spell in the game for dealing with sudden spike damage when you REALLY need to get that big heal off. Druids and shamans need NS in their healing builds to even come close to the disaster prevention that little bubble offers. Doesn’t absorb much, but just enough to get a big 3s heal off.
As for damage spells, basically depends on your build. Holy priests spam Holy Fire and Smite. Shadow priests don’t touch it. Personally, I train everything always cause I dislike sorting through tons of spells at the trainer to pick and choose. But that’s me.