Hi Tekshu, I'm 112 too and my setup is based on P. Skill Critical Damage, it's more expensive than just P. atk Critical Damage but it works better for me.
In my case, I first raised the buff skills and then the damage skills (I'm still raising them).
What I was looking for with the soul crystals was to raise the P. Skill Critical Damage as well as with the argument (I was lucky and I got +20% P. Skill Critical Damage).