Easy Expert Level - Guide for Kingdom Hearts

When you first start, you can fight Riku, Wakka, Tidus, and Selphie by talking to 
them. A good way to get experience is to fight Wakka or Riku, however if you defeat 
them all and get the items you need for the raft (the two logs, the cloth, and the 
rope) and select "Rest", when you wake up in the morning you can fight everyone 
except Riku. Defeat Wakka and Selphie then talk to Tidus. He will tell you about his 
three on one match with Riku and how bad he lost. You will then have three options, 
Select "3 on 1", and you will start fighting against Wakka, Tidus, and Selphie. 
Tidus and Selphie attack in a group. Knock out Tidus, then Selphie. Keep your 
distance from Wakka. When he throws the Blitzball at you and it is about to hit, 
slash your sword. It should be deflected, and you will get 1 or 2 experience points. 
You can repeat this as many times as needed, but if you hit Wakka with the ball a 
certain amount of times he will die. Even though it may take practice hitting the 
Blitzballs, it is the easiest way to get experience at the start of the game. It is 
possible to leave Destiny Island at level 12, almost strong enough to defeat Cloud.