I got about 100k increase, and went from trying to get over 500k now closing in on 600k.

each individual ninja is going to give a boost to a stat and initiative and a lot of ninja are not the same as others. compare GNW Neji vs Sage Jiraiya vs Rinne Sasuke

start going thru all you 1-star / 2-star / 3-star and any 4-star ninja that you can upgrade to the next lvl.

i found that upgrading stars gives more in return, the awakening will give you single digit numbers, while the upgrading stars will give you double digit or triple digit numbers

i.e.

awakening will give you 1-9 in power increase

stars will give you 10-199+

it is hard to gauge which ninja will give you the biggest return on star upgrades, but seasonal and rare ninjas are obviously going to give you more

I spent my time upgrading EVERY single ninja in lvls and have yet to increase all their awakenings, but i have and got another 6k more after the initial upgrade in power.