So. I leveled a priest, and this is my "helpfull" advice. The first 10 Points goes into spirit tap and then wand.
Then take 2 Points in improved shadow wordt death, Then til level 40, Go take stuff in disc. Shadow does not offer you enough, you dont need to get mindflay, a waste of taltents since before shadow form it's useless.
After 40, you can respec intil Full shadow, and then ofc your first few taltents will be into wand.
Be mindfull of where to get new wands, they are your most important item, it pretty much as important for a priest to get a wand , as a warrior to get their weapons, It your everything.
When you level, Preshield, cast 2-3 smites and a Shadow word pain, and then wand.
maybe less smites if you feel like you are useing to much mana.. It a balance between Your health From wanding to long, and Spending to much mana casting spells.
Rule of Thump if your at 100% of anything you are not pushing hard enough