Hey fellow Final Fantasy X explorer! When it comes to sphere grid progression, focus on unlocking key abilities like Quick Hit for Tidus, Overdrive -> AP for Rikku, and Flare for Lulu. Don’t be afraid to mix and match character paths to make them versatile in battle.

For side quests, definitely tackle the Monster Arena for great rewards and tough battles. The Celestial Weapons quest is a must for powering up your party. And don’t forget to hunt down all the Al Bhed Primers for a special surprise!

In terms of character builds, customize each character to their strengths. For Tidus, prioritize agility and speed nodes. For Auron, go for strength and HP. And for Yuna, focus on magic and evasion. Experiment with different builds to see what works best for your playstyle. Happy exploring!