What would be the best possible inner potential for mages?

Just look and see what cost the cost and there you go. Money, money, money!

I'm not sure what you're trying to say. If you're implying inner potentials can be bought, they cannot, sadly. If you mean cubes, I don't have much to spend for them anyway.

edit: if you're somehow trying to change the topic of this thread into a political one, wrong section bro, lol.