Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, focus on unlocking key abilities and stats for each character first before branching out. Don’t be afraid to backtrack to previous nodes to grab important skills. For side quests, make sure to complete the Monster Arena challenges for valuable rewards and tough battles. Additionally, don’t forget to collect the celestial weapons for each character by completing their respective side quests. As for character builds, tailor each one to fit your playstyle. Experiment with different paths on the sphere grid to maximize their strengths in battle. Happy exploring!