Hey there, fellow Final Fantasy X explorer! When it comes to sphere grid progression, my tip is to focus on unlocking key abilities and stat boosts first before branching out. This will make your characters more well-rounded and powerful in battle. Don’t be afraid to backtrack to previous nodes to grab important skills!

For side quests, make sure to tackle the Monster Arena challenges for valuable rewards and tough battles. Also, don’t forget about the Celestial Weapons and their corresponding side quests for each character. They are a bit challenging but totally worth it for the powerful upgrades.

In terms of character builds, think about each character’s strengths and weaknesses when choosing where to allocate your sphere levels. For example, Tidus is great for agility and speed, while Lulu excels in magic. Experiment with different paths to find the best build that suits your playstyle. Happy exploring!