Leveling up Legions
Make sure to level up one organic-attack Legion and one inorganic-attack Legion (for example, Guilt and Flawed) until stage 9. After that, you can go back and level all of your Legions equally.
Blasphemey and Hatred Legions are by far the hardest Legions to level up. Take out one of your more powerful Legions along if you are using either one of them.