Finite Stones

I wouldn't upgrade anyone. It's easy to lose fights when you have less hearts. Check the threads if you want more information on this strategy but basically- every time you lose you get at least 55 knuckles plus a bonus of at least 8. I've got twelve characters so I get 9 to lose and if I play it right sometimes even more. So every 4 hours that another 495 knuckles at least in addition to the 350 (plus bonus) I'm getting for the winning the 3 fights. I don't know how many more knuckles you can get for upgrading but just doing it my simple way- I'll get Old King Coal and be done crafting by the end of today. (Leaving me like, what 9? 8? days still?).
Also using this tactic I never have to used band aids or energy drink. I use that all for fighting people in my neighbors towns.
Hope this isn't confusing!