Focus a majority of stat allocation into magicka, but give yourself a little health for survivability; a dead healer is a useless healer. Wear light armor to compliment magicka. Look into the restoring light skill tree of Templar, but don't forget the restoration staff skill tree. Be mindful that while leveling, you should have one skill from each of your class' skill lines in your bar, and you should also wear one piece of medium and heavy. This will give you more options to choose from at end game without having to level stuff.

Cheers.