Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, my tip is to prioritize unlocking character’s key abilities first before branching out. This will make them more versatile in battles. Don’t be afraid to backtrack to grab important nodes like HP and MP boosts.

For side quests, definitely don’t miss out on the Celestial Weapons and Aeons quests. They provide powerful gear and extra challenges that are totally worth it. Also, don’t forget to participate in blitzball matches and monster capturing for additional rewards and stat boosts.

As for character builds, focus on customizing each character to their strengths. For example, Tidus can be a speedy physical attacker, Yuna can specialize in white magic, and Lulu can be a powerhouse black mage. Experiment with different abilities and see what works best for your playstyle. Happy exploring!