Blood Mage - Blackflame Fireball

Hello everyone. If anyone plays this build or just knows what's best to take, please advise which buffs are best to take in Act 3 Normal and Cruel. As the title says, I play through Blackflame Fireball. The guide I'm currently following doesn't mention this, but another build recommends taking 25% increased Stun Threshold and then +10% to Chaos Resistance.
But wouldn't it be better to take mana regeneration in normal mode?

Don't most of the builds end up taking Blood Magic or using the Blood Magic unique helm? This means you no longer have a mana pool because you're using your life to cast spells.

No, BMs have double the cost of their spells; split between the spell's mana cost AND a life cost.