Entering Guadosalam will have someone named Tromell Guado greet you, who mentions that Seymour is waiting for Yuna at his manor. While everyone is walking away, Rikku will unlock the ability to customize your equipment. Similar to granting new abilities for Aeons, you will require to expend items in order to learn new auto-abilities for your weapons or armors. Of course, not every piece of equipment can be customized (like Tidus’ Brotherhood, as an example), and you will need an open slot on the equipment. Unfortunately, there’s really not much you can add right now, so it’s best to save items for later.
After tinkering with the customization options, the first doorway nearby leads to the inn, where you will find a Save Sphere. Maechen is also here, in case you want to learn about the Farplane or the pyreflies. Exit the inn and go to the manor’s entrance straight ahead, although you’re not going inside just yet. To the right of the entrance is a chest, so open it for a Mega-Potion. Follow the western wall and enter the first building you come across, where there will be Al Bhed Primer Vol. XIII on the ground inside, as well as a chest in the back, containing 3,000 Gil.
Exit this building and continue following the western wall south, to two NPCs speaking by a lamp. Squeeze past them to find one more chest, with this one holding an Elixir. Up the ramp will be the entrance to the Farplane and if you go underneath it, you will find the shop. O’aka will also be in the shop and his goods, depending on if you’ve donated the full amount needed, will be cheaper than the actual shop’s wares. Note that you will be visiting the Thunder Plains next, and as the name suggests, you might want to purchase the Yellow armor for your characters. There’s nothing else here, so head inside Seymour’s manor.
Climb the stairs and search around in the middle until you open a chest that has two Hi-Potions. On the left set of stairs is Wakka, so speak to him, then go to the right side to speak with Lulu, which will trigger a scene. Feel free to speak with the others downstairs, then approach the double doors for another scene. Speak with everyone inside to trigger another scene. Exit the manor once that finishes and meet up with the rest of your party. You will be heading to the Farplane now, which is up the incline in Guadosalam. As soon as you enter the next screen, look to the left for a hidden chest that contains 8 Lightning Marbles.
Continue along to the entrance of the Farplane, then go in it. Once you gain control, speak to Lulu, then Wakka and Lulu once more. To get the story moving again, approach Yuna and you will be finished with the Farplane. After returning to Guadosalam, go back to the area in front of Seymour’s manor to meet up with everyone, then they will all split up as they wait for Yuna. Feel free to talk with everyone, although you might want to speak with Lulu twice. The choice here doesn’t really affect much, except for a scene a little later in the game. Note that Kimahri will appear as you attempt to go inside the shop.
Note: Tidus’ Brotherhood weapon will receive some extra buffs to it after the Farplane scenes. In addition to the initial Strength +5%, it will gain Strength +10%, Sensor and Waterstrike.
To get on with the main story, approach the exit near the beginning area (the decline that is guarded by a NPC) for a scene with Shelinda. Meet up with the party afterwards, in front of the manor, then it’s time to make a move on to the Macalania Temple. In order to get there, you’ll have to pass through the Thunder Plains, the next stop, but before that, there is one final treasure you can get here. Return to the Farplane and in the area itself, there will be a chest on the left side, which holds the Venus Crest, an item needed to power up Lulu’s Celestial Weapon. The decline where you met Shelinda just before is the exit to the Thunder Plains.