hey, a level 40 noob here. Great to see there are fellow free player who's striving to win against paying players. I've been having the same idea of saving for stat upgrade and buying them all in one week's time, since that's one of the only areas where paying players don't have an edge over - maximum amount of stat upgrade is determined solely by level.
I've looked up the total stat upgrade leaderboard, and I noted that the top all time stat upgrade max is capped at around 23k, while the top weekly stat upgrade is around half of that. So I'll just have to save and save and save until I reach level 300ish, and spend it all in one go! The long term koban payout probably isn't worth it (considering a better stat would allow easier fights in leagues), but why not? I'll show them what a determined free to play player is capable of!
I'll update you when I reach level 300ish, which could well be years or centuries later haha