In reality all of the above are right and wrong at the same time. I don't know what's your current position or stats, but a real indicator should be top of the bracket you are currently in (or if you aren't in the top, those people you want to compete with). 20k secondary stats might be good for now, but in the future, let's say 1 year it may be an average. Absolute top of china has over 40k ini right now for referrence.

Whats pretty obvious you should upgrade all basic power features (keys, refines, charms, maybe treasured tool?) to max, after that personal ninja growth depends on pills and chakra training as of now, and its hard to upgrade much further. That means you'll be able to use refines, keys etc on other positions, while polishing your move1 with those hard-to-get items. Other means of improving power are team wide like myobokus or clothings, so if you decide to go for them it means you are improving everybody anyway.