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 great rewards and tough battles. Also, don’t miss out on the Celestial Weapons and the optional Aeons for some extra firepower. As for character builds, experiment with mixing different paths on the sphere grid to create versatile characters. Try to specialize each character based on their strengths, like physical damage for Tidus and magical prowess for Lulu. Happy exploring!