Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, I recommend focusing on acquiring key abilities for each character first before branching out. Don’t be afraid to backtrack on the grid to grab important nodes. For side quests, be sure to complete the Monster Arena challenges for great rewards and unlock ultimate weapons. Also, don’t forget about the celestial weapons and the optional Aeons. As for character builds, tailor each character to their strengths – like magic for Yuna, speed for Tidus, and strength for Auron. Experiment and have fun customizing your party’s abilities!