As much as possible for the least amount of harm possible and the least amount of wasted time and resources, obviously. Which varies on a case by case basis.

I mean if it was practical, you'd give your friends 2 billion units of happiness, and then after turning the cheek to your enemies, grant them 1.9 billion units of happiness, but living on planet earth, giving you 80% of the crap you gave me seems about right.