Boss readiness is easier to judge when you separate damage from the systems that let you stay alive long enough to deal that damage.
Movement is part of readiness
If you cannot consistently reposition around attacks, improving mobility may create more value than another small damage increase.
Arena space reduces avoidable mistakes
A clear arena removes terrain problems and gives your current movement options room to work.
Recovery should be planned before the fight
Healing and other consumables only help when you know when and how you can create space to use them.
Change one weak point at a time
After a failed attempt, identify whether the main issue was movement, survivability, damage uptime or unfamiliar attack patterns.