Final Fantasy X is a video game from Square Enix that mixes tactical battles with open world adventuring.
GAMEPLAY HINTS
Defeating the Spherimorph
Use Yuna's second Aeon. When Spherimorph uses a fire attack, it well give him life. Then, attack him. If he uses any attack that takes away HP from your Aeon, then use fire on the Aeon. You will eventually defeat him.
Summon Ixion and attack. Every turn, Spherimorph will cast Lightning. Then, either use Press or just attack. The lightning will heal you, then Spherimorph will hurt and you will never die.
Have Lulu, Yuna, and Rikku on your team. Have Rikku attack to find out which element it is using. Then, have Lulu cast the opposite of what it is using (fire, use ice; water, use thunder; ice, use fire; thunder, use water). When your party's HP gets low, have Yuna heal your team. When Rikku's Overdrive is full, use Mix. Mix a Map and a Lunar Curtain. This will make a Mega Nulall. When it uses a spell, your team will not get hurt. Have Lulu cast spell to defeat it.
Defeating the Stratoavis in the Battle Arena
Once you collect all the monsters from the desert, go back to the Calm Lands and go to the Battle Arena. If you have caught all of them, the man will offer you a free fight with the new monster he just created. Accept his offer. Once in the battle, make sure you have Yuna in your party. Wakka and Tidus are also recommended.
To make this faster, you will need the Aeon Yojimbo. He can dodge all the attacks from Strutoavis and put Yojimbo in Overdrive. This should enable you to pay a low price for maximum damage. You should be able to pay 10 to 20 gil and he will do one of four attacks. If he does Wakizashi or Kozuka, it should do maximum damage. Do this about fifteen to twenty times and he should fall. You should get about 10,000 AP for winning, and perhaps a Key Sphere.