Moonflow

Follow the trail north until you meet up with Shelinda. After talking to her go into an area behind her to get 3 Lv. 1 Key Spheres.

Then continue until you meet up with Biran and Yenke Ronso. Open the chest nearby for an X-Potion. Keep moving along the path on the lookout for another small alcove with 3 Lv. 1 Key Spheres.

Then continue on the path until you come across Belgemine. She'll challenge you to a fight against Ixion. You'll want to use Ifrit. Have him start out in overdrive and then use Fire to cure as necessary. When Ifrit trances the second time use it to finish off Ixion. For winning you'll get 2 Dragon Scales and, win or lose, the Summoner's Soul which allows you to teach aeons new abilities

After the battle continue along the path until you find a small path to the left. Here you'll find a Magic Defense Sphere. Then continue along the main path to the wharf.

O'aka is here with a full inventory. Also the chest here contains 2 Phoenix Downs. Then move to the next screen.

Here speak to Auron and then go left. After talking to the Chocobo Knights go up onto the platform in back to collect 5000 gil from the chest. Also maechen is here with a history lesson. Then speak with Wakka & Lulu. After that go back and find the Hypellow who lets you ride the Shoopuf.

If possible equip Tidus and Wakka with Lightningstrike weapons. Have Tidus cast Haste on himself and Wakka and then just attack. Use a Hi-Potion or Potion if needed.

After reaching the North Wharf use the save sphere and then go left. Here you can buy items from O'aka. Also, Al Bhed Primer Vol. XII is right above O'aka on the platform.

Now go left to start dopwn the trail. Right away you'll find a chest with an Ether.

As you move along the path you'll be reunited with Rikku and she decides to join your party. You'll also get tutorials about her steal ability after you continue on the path.

Along the path to Guadosalam you'll find two more treasure chests with 4 Antidotes and a Mega-Potion.