Hey there, fellow Final Fantasy X explorer! When it comes to sphere grid progression, my top tip is to focus on unlocking key abilities early on, like Quick Hit for Tidus and Doublecast for Lulu. For side quests, don’t miss out on the Celestial Weapons and the Monster Arena challenges for some epic rewards. As for character builds, I recommend customizing each character’s path on the sphere grid to maximize their strengths. Experiment with different abilities and see what works best for your playstyle! Happy exploring!