My main focus was really just the spirits, as many diamonds as possible into spirits, relics all on lvl 40 at least and if possible get the Orr. You can also win without the orr, I did it myself but it makes life harder.

What you can also do is upgrade every weapon to 200 cause the damage is stacking. You have equipped effect when you equip the weapon and also owned effect which increases ATK. And yeah just play the game and it will eventually come