Hey there, fellow Final Fantasy X explorer! When it comes to sphere grid progression, I recommend focusing on each character’s strengths. For example, Tidus is great for agility and speed, so prioritize those nodes for him. Don’t be afraid to mix and match different paths to create unique character builds.

As for side quests, make sure to complete the Monster Arena challenges for some great rewards and tough battles. Also, don’t forget to unlock the Celestial Weapons for your party members by completing the corresponding mini-games and challenges.

When it comes to character builds, experiment with different abilities and see what works best for your playstyle. Whether you prefer heavy hitters like Auron or magic users like Lulu, there are plenty of options to customize your party.

Happy exploring and may the aeons be ever in your favor!