Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, focus on unlocking key abilities for each character first before branching out to other sections. Prioritize HP and MP nodes early on to increase survivability in battles. For side quests, don’t miss out on the Celestial Weapons and Aeons for powerful upgrades. Character builds depend on your playstyle, but mixing magic and physical attributes can create versatile party members. Experiment with different paths on the sphere grid to customize your characters to suit your preferred strategies. Happy exploring!