Final Fantasy X is a video game in the well known JRPG series from Square Enix.
GAMEPLAY HINTS
Defeating Sinspawn Gui
Destroy the head first, so he does not do much damage. Next, destroy both his arms. Have Auron and Wakka in your party. Auron can destroy the arms and Wakka can destroy the head. The head just has 1000 HP and the arms have 800 HP. Do not change Auron because the arms will regenerate. When you fight Sinspawn Gui 2, you will have Seymour in your party. Have Seymour use Thundara on the head.
Next, have Yuna summon an Aeon with its Overdrive (if available). If not, just do the same thing as last time without Wakka in your party. Also, use Seymour's Thundara ability on the body, which has 6000 HP, to destroy Sinspawn Gui 2 faster. Remember to take out the arms first.
Have Lulu use Fira (recommended) or Fire on the head. Once the head is taken out, have Lulu use Fira on the body and Tidus use Cheer to increase the attack of your party members.
Defeating the Spectral Keeper
Have your Overdrives full and use them. You should have between 4,000 to 6,000 HP, Aga magic, lots of curing items, and Protect (to muffle the power of the Boss' moves). He does a move called Glyph Mine that kills you instantly. Getting hit by this is pure luck. He normally only does it one to two times.
Make sure all your Aeons' Overdrives are powered up before the fight. Have Tidus, Yuna, and Auron in your party. Have Tidus cast Haste on Yuna, then have Yuna summon her Aeons as quickly as she can. After each Aeon uses their Overdrive, the Spectral Keeper will probably use Glyph Mine on it, killing it instantly. If not, just have it keep hacking away at it as much as it can, healing itself when necessary. You can keep Tidus and Auron in there to heal Yuna, or you can swap them out for other characters to get them some experience.