I don't like that in the ability you need to spend your growth on it and it's so hard to gain experience for growth.
The best way to grind xp is to get the sword that Bunshido has and grind xp from the bandit boss but make sure you have enough size sourced from essence and spend all of your growth from leveling because if you are level one you get more than 100 levels each fight to use to unlock abilities. You also get a ton of skill points from the fight. Also I recommend getting the Mad Chimera follower because she is op