One good thing about hunting monsters, they're basically walking mana batteries for me.
While my summons attack the monsters we find in the dungeon, I would take the opportunity to create maximum stats summons at the back of the fight.
Once the monsters are defeated, I'll have my summons collect the Mana Crystals and replenish my mana that way.
The downside to this arrangement is that only my Magic stat is increasing since I'm not training myself physically, but having more summons makes it worth it.
Of course, I didn't use up all the Mana Crystals I collected and kept a few in my backpack just so that I get a net profit in terms of Mana Crystals for later use.
The curious thing is that despite being able to transform the mana inside these Crystals to other elements, I have yet to gain the magic skill in said elements.
