Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, make sure to prioritize unlocking character’s key abilities first before branching out to other sections. Focus on increasing stats that complement each character’s role in battles. For side quests, don’t forget to complete the Monster Arena challenges for rare items and AP. Also, aim to acquire the Celestial Weapons for each character by completing their respective side quests. As for character builds, consider customizing each character’s grid to maximize their strengths. For example, focus on magic for Lulu and physical attacks for Tidus. Happy exploring!