Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, focus on unlocking key abilities and stat boosts for each character. Don’t be afraid to mix and match different paths to customize your team to your playstyle. For side quests, make sure to complete the Monster Arena challenges for valuable rewards and tackle the optional Aeons for extra firepower in battles. As for character builds, consider specializing each character in a specific role like tank, healer, or damage dealer to create a well-balanced party. Happy adventuring in Spira!