Without a healing spell, Barrier is the most important. I take the first spell in all the elements except that stupid fire spell, I trade it in for Immolate? (The one that acts like fire bomb). Chain Lightning is the best AOE spell (low cost, high value). With the exception of upgraded Barrier, I don't use the Spirit spells (I play on Hard not Nightmare so...), I usually grab the two passives from Immolate that get me down to the wall of fire spell. In fact, I give all my mages the initial elemental spells and then put the remainder in their specializations.
If I want to be invincible, I specialize in Knight Enchantment. Frankly, I was underwhelmed by the spells this time.
I really miss the old DA:II Force spells. (Some of these spells bear the same name but don't do as well). I used to love being a controller mage in DA:II and use Anders as Nuker.
I also miss Origins Walking Bomb. Origins explosion was a hoot. The new one isn't nearly as much fun.