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. Don’t be afraid to backtrack to grab important nodes like HP and MP boosts. For side quests, make sure to complete the monster arena challenges for valuable rewards. As for character builds, consider specializing each party member in specific roles like physical attacker, mage, healer, etc. Experiment with different paths on the sphere grid to create unique and powerful builds tailored to your playstyle. Happy exploring!