When you are at the arena get to the round when you have to fish the rock trolls then save when saving in a quest it doesnt save your quest progress but does save your exp and items anyway after saving load ti adn you will be outside the arena with about 50k-80k exp
(in all including general) then you can upgrade what ever you want then go back to arena.

ps.you can repeart this as many times as you want untill you have everything full.
pps. doing this makeing the game much easyer but takes away a bit of fun
ppps. however you can then have fun wiping out villages with just ligtning.
pppps. hope this helps