Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, I recommend focusing on unlocking key abilities for each character first before branching out. Use clear spheres to remove unwanted nodes and create efficient paths for your characters.

For side quests, don’t miss out on capturing different monsters for the Monster Arena and completing the Celestial Weapons quests for some powerful gear. Also, make sure to participate in the Blitzball tournaments for unique rewards and a break from the main story.

As for character builds, try to specialize each character based on their strengths. For example, Tidus can excel as a physical attacker, Yuna as a white mage, and Lulu as a black mage. Experiment with different abilities and mix and match to suit your playstyle. Happy exploring!