Fast answer
Capsules are strongest when the copies they give you feed a line you were already building.
What makes Capsules valuable
Capsules are not only about rarity. Their real value is how often they turn into:
- better evolution progress
- a stronger main team
- clearer roster decisions
Best player habit
Open Capsules with a reason. That reason can be “I need a core team” early on or “I need one more copy of a keeper” later on.