Each student has an EX Skill, a Basic Skill, a Passive Skill, and a Sub Skill. Prioritize upgrading the EX Skill first, as it's manually activated and often the most impactful. Next, focus on the Passive Skill, which provides constant stat boosts. Basic and Sub Skills are important but generally take lower priority unless they have a unique, game-changing effect. Use 'Blu-rays' and 'Technical Notes' from the Joint Firing Range to upgrade skills.
