I use a beastmaster life / earth warrior build.  Beastmaster is awesome in that you can tame a ton of monsters.  It's a huge boon early game.  Life / earth give Growth and Giant form, which combine (probably a bug right now, but it's awesome) to give some absurd bonus that ends up being like x10 at higher levels.  I'll have >800 attack once my sovereign is fully leveled and buffed with those 2 spells.

Sounds like an awesome bug but why would you use units if you do 800 damage a swing?

I could always help with a build for sovereign, but I do not understand what you want with your sovereign.

I usually focus my own sovereign on the magic type I usually want to use, if I want to level my heroes I pick air due to the enchantment "Tutelage", if I want to play a game with a blaster hero, I pick fire, and usually just pick "Earth" due to the Enchanted Hammers spell...

Right now I will hold back any major guidelines or anything, since strategies change from beta to beta.
The game balance is far from done, so each build might be obsolete in the next balancing patch.

Sincerely
~ Kongdej

Also Air 2 gives a city enchant called "Aura of Grace" which is quite powerful in 0.952.
(+2 initiative per essence in city to trained units).
This becomes even better with the Pariden factions ability to produce +1 essence in each city, although Pariden units are fairly weak without shards or other boosts.

Sincerely
~ Kongde