Which Chansey should I prioritize to put in gyms?

Any Chancey that have high hp and def stat. You don't expect this eeg shape to kill someone, do you?

You can save candies for blissey too

chansey make 0damage, you need use the timer for win.
the best move set for that, is pound/hyper beam
(Some player spam dodge when see 1 Cast Hyperbeam and Wasted many seconde)

IV of defense and Stamina? That is what is important!

Chansey doesn't win. It times out opponents!

Go for hp. I went hyper beam as well hoping people would dodge out of habit to kill extra time. It will not kill the attacker no matter the moveset. I made a post yesterday about my test against maxed chansey.