How much fire damage does Inspiration add?

The 16% covers the whole team's fire damage, not only Spark Elf's own hits. That makes Spark Elf a support pick. It does the most good when the rest of your party is built around fire, and it does nothing for a team that hits with water or other elements.

Because Inspiration is a core skill, Spark Elf does not need to stay on the field to use it. In Egg Heist you can call on a benched Aniimo's core skill by switching to it. In Holo Battle Interlink, the second to fourth slots can use their core skill but not their second skill, so Spark Elf still brings Inspiration from an assist slot.

For comparison, Turbo's core skill raises team damage and break efficiency by 15%. That bonus works for any element. Inspiration is the bigger number, but only fire benefits from it. Both skills draw on the energy pool your whole party shares, so every cast leaves less EP for the rest of your rotation.

Not settled: The 16% is a fixed figure for Inspiration's fire bonus. How long it lasts, and whether it stacks with Turbo's 15% team damage bonus, is not covered here.