Quick Answer
Use regular or advanced balls for common spirits and routine index completion. Use a specialized ball when its current item description matches the target or condition. Save King Balls for rare spirits that are difficult to encounter again and Prism Balls for spirits whose chromatic appearance you genuinely want to keep.
King Ball vs Prism Ball
Public launch guides describe both as guaranteed capture options that secure the top talent rating. A Prism Ball additionally creates a random chromatic appearance. Chromatic is not the same as a rare alternate-color spirit: a Prism Ball does not turn a normal spirit into an alternate-color one.
A Resource-Safe Order
Confirm the target in the Spirit Index, check the current capture prompt and obedience limit, then choose the least scarce ball that fits. Use regular balls for repeatable common targets, advanced balls for more reliable routine captures, specialized balls when their conditions match, King Balls for rare keepers, and Prism Balls only when the chromatic result matters. Check Item Data for current descriptions.
Exact rates and acquisition channels differ across public guides and may change by season, so current in-game item descriptions take priority.