Honestly man it depends on what ninjas you wanna run for the rest of your game experience.If you're gonna be that guy who only ever uses edo hiruzen or ashura naruto just keep on stacking pos1, no point in raising your other ninjas if your pos1 will just carry entirely no matter what. But that gets boring so yeah around 20k stats for at least those first 3 (ini,injury and critical) if you wanna run other teams and not get have your other 3 positions 1 shotted.