I've seen this complaint come up a few times - basically, 1MP a turn is too little to power any sort of long term spell heavy strategy with your Sovereign. This is quite true, and I think it's something that probably needs to be addressed, but however they change it, I can't see MP ever being an unlimited resource, unless they heavily tinker with the power of strategic and tactical spells (or possibly separate the mana pools they utilize).
In any case, with the game now, here's what you need to do:
1) Make babies!
The dynasty portion of the game isn't really pushed on you much in the game, but here's the deal - find a champion of the opposite sex, marry them (under the Actions tab), and stick your spouse safely in a well defended city. New children will automatically be born.
Now the important point - your kids retain your attributes! They are also all full fledged channelers. Equip them, level them up, and then let them run riot as army leading spellcasters.
Remember that you can also research Diplomacy techs to arrange marriages with AI civs, giving you a diplomatic bonus and even more children.
2) Imbue Champions
Hire new Champions, equip them well, level them, and imbue them with your essence. This takes some of your essence and transfers it to the champion, making them a mobile caster. They probably won't be quite as strong as your children, but they can make good use of utility magic. I'd recommend gaining them a few levels first, before imbuing them - losing an imbued hero is a painful loss, and there's no Resurrection spell that I know of.
3) Research Magic
This is a late game perk, but by continuing to research Magic techs past the 'end' of the tree, you can gain permanent Essence bonuses to all of your hero units.
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There is one unique structure that increases MP regen, as well as a structure that boosts unit Essence, but they are also late game. The main thing is to get more units that can use magic, because each new caster hero you acquire increases your MP/turn rate. If you only use your Sovereign the entire game, your regen rate is 1/turn. If you've got 10 heroes, you're earning 10MP/turn of usable mana.
