How to power up

To begin with, don't do it the way I do. I'm all over the place with the result I have very few grade A defenders maxed out.

Keep your best defenders maxed out at all times. They're supposed to constantly be inside a gym, so they really should be as good as possible.

At the beginning of a new level this just isn't possible. You need your mons inside gyms, and placed there you can't power up them. Well, gyms go down. When you get one back give it your love twice and it's ready to go for the rest of the level.

When you're building new pokemon from comparatively low cp, focus on your defenders. They're your future capital.

However, sometimes you just need a new attacker due to shifts in the game. It can be a patch like last autumn, or it could be a change in your local metagame. Still, an attacker seldom needs to be maxed out. After all you get to pick your attackers when going after a gym.

Apart from a few attacking stars I'd settle for stopping after the relatively cheap 5000 stardust and 4 candy.

So, how many pokemon should you groom? Well, not the 37 I'm looking at. There's a reason I'm currently having trouble maxing out prime defenders. I think half a dozen attackers and a dozen defenders should do just fine. Lower that number by one or two for each level below level 36.