You start off in the Oasis of the Bikanel Desert once you regain control of Tidus. Start off by saving your game at the Save Sphere and then jump back into the water to grab a treasure chest on the lower left side of the pool that contains four Remedy.
Walk forward into the desert and you will be thrust into battle against a Zu - the giant bird-like creature. Tidus starts off all by himself at the start of this battle and will be joined partway through by Auron. Lulu will join the battle shortly after that. Using Haste on Tidus (and your team members) and using Slow on Zu can make the battle significantly easier.
Continue northward to find Wakka sitting under some scrap metal. The treasure chest beside him contains an Al Bhed First Aid Kit which will allow you to obtain Al Bhed Potions from treasure chests in the area. There may also be an Al Bhed Primer near Wakka if you have missed any of them thus far. Continue northward when ready.
Note regarding Al Bhed Potions:
They can only be used by Rikku using the ‘Use’ command. They heal for 1,000 HP and remove the Poison, Silence and Petrification status effects. This means that Rikku can act as your interim healer while you are missing Yuna.
Sanubia Desert - East
Head into the little alcove to the right to find Kimahri. Head backwards once you have met up with Kimahri and head around the dogleg and continue following the trail until you run into Rikku.
The treasure chest next to where you find her contains two Ethers. Do not forget to save at the Save Sphere which is essentially a free opportunity to heal up your players now that your primary healer is missing.
Follow Rikku in behind the scrap metal. During your first fight with Rikku back on the team you will get a quick explanation of how using the ‘Steal’ command on an Al Bhed machina will destroy it in one hit.
There will be a noticeable area that extends off to the left as you continue down the pathway. Following it will lead to a treasure chest that contains four Hi-Potions. Continue along the trail into the next area.
Sanubia Desert - Central
You may eventually run into a Cactuar in the area. Cactuars are a tough enemy. They have very high evasion and heavy armor, which means that even if your attacks do manage to hit the Cactuar they will do very little damage. They also unleash some pretty devastating attacks including 10,000 Needles which does 10,000 HP worth of damage - making it an instant kill.
On the opposite end, they give great rewards for defeating them, including armor and weapons as well as a very large amount of AP. The best tactic for defeating Cactuars is to save up your Overdrives during your time in the Bikanel Desert and use them if you run into any Cactuars. Your Overdrive attacks cannot miss.
Follow the red arrow into the center of the next desert section. There is a treasure chest in the center of this area that contains four Hi-Potions. Just south-west of this treasure chest is a rock formation that is shown on the mini-map. On the opposite side of the rocks is a treasure chest that contains two X-Potions. Finally, at the far west corner of the map there is a treasure chest that two Mega-Potions.
Make your way to the Save Sphere located north of all of these items. The sign next to the Save Sphere reads “Beware of fiend! Weaker fiend to the right. Stronger fiend to the left.” Go west from the Save Sphere into a small enclosure and you will find a treasure chest that contains an Elixir (to the south) and the enclosure to the north of this area has two treasure chests - one of which contains a Lv. 2 Key Sphere and the second which contains 10,000 gil.
Just north of this area you will find an Al Bhed Primer (vol. XVII) sitting on the ground.
Go back to the save point and head straight north towards a sign post in the distance. Lying just below that sign post is a book - Al Bhed Primer vol. XVIII. Continue north from here into the next area.
Just in case you are curious - there were two paths leading northward in the last area and they both lead to this same region so don’t worry about leaving any of the areas unexplored.
Sanubia Desert - West
Continue north through this region until you see a small area off to the left side on the mini-map. There is a treasure chest along the way that yields eight Hi-Potions. West from there, at the bottom of the sand whirlpool, is a treasure chest which contains the Mercury Crest. This item is needed later on to obtain Rikku’s Celestial Weapon, the Godhand.
Northeast of this area are whirlpools with treasure chests inside of them. Once you touch the treasure chest you will be thrown into battle against a Sangragora. Sangragora are relatively easy to defeat other than the Confuse status effect that they can inflict on your party members. Al Bhed Potions which Rikku can use are capable of removing the Confuse status effect in addition to healing party members.
The first treasure chest contains three Megalixirs. The second chest contains two Teleport Spheres. Read more about Teleport Spheres in the Sphere Grid section of the strategy guide. Just northwest of this area is one last treasure chest which contains two X-Potions. Go north into the next area of the zone as the area east of here is “blocked by a sandstorm”. You will have to fight one last Sangragora that blocks the path.
Along the left side of the screen you will find an Al Bhed Primer (vol. XIX). You can also pick up two Hi-Potions off the corpses of the dead Al Bhed soldiers. Save your game using the Save Sphere off to the right side of the doorway. Go through the front doorway when you are ready.
Your first fight will be an ambush against one Guado Guardian and three Bombs. Start by taking out the Guado Guardian. Use Rikku’s ‘Steal’ or ‘Mug’ ability to steal a Hi-Potion from the Guado Guard thus preventing it from using its ‘Auto-potion’ ability and healing itself. The Bombs can be defeated like similar to normal fiends - focus on one until you destroy it. If they manage to grow three times they will use their ‘Self Destruct’ ability which only damages for 1,000 HP. A much more manageable hit at this stage in the game.
Go forward through the only doorway that you can enter. The next fight is similar to the previous one. Focus on the Guado Guardian and then take out the two Dual Horns. There is a chest just off to the side of the pathway that contains four Al Bhed Potions. Hit up the Save Sphere and save your game before you continue.
Home - Main Corridor
The area that you are in has three separate pathways with the Save Sphere being located in the left most pathway. Use the mini-map to make sure you are in the right location. Head down the middle pathway to find a treasure chest that contains six Al Bhed Potions.
Before you go down towards the forked pathway leading to three separate corridors, turn around and head back up the stairway. There is an additional room called the Living Quarters that is marked by a green square on the mini-map. Go through the doorway and you will be ambushed and thrown into a battle against a Guado Guardian and two Dual Horns. Pick up the Al Bhed Primer Volume XX on the bed after the battle.
Take the right pathway and you will find Al Bhed Primer Volume XXI lying on the ground. Enter the doorway and you will be thrown into battle against a Guado Guardian and two Chimeras. You will have to break the password in order to open the Al Bhed chest inside this room. You will likely be able to read most of the text displayed below if you have been following this guide. The actual numbers will change each play through, but math will stay the same. The Al Bhed text reads:
The first digit is _ plus _
The second digit is _ minus _
The third digit is _ times _
The fourth digit is _ plus _
Open the Al Bhed chest to receive a Special Sphere. There is also another Al Bhed Compilation Sphere on the ground which you can use to load any previously discovered Al Bhed Primers in other save games that you have directly into this one.
There is one more Al Bhed chest to the right of the one with the password. It reads “Al Bhed Verification” in Al Bhed when you press ‘X’ near it. Just in case you did not pick up enough Al Bhed Primers, the answers are:
1) Are you Al Bhed? Yes (third answer down)
2) Name the son of the Al Bhed leader. Brother (fourth answer down)
3) Oh what island do the Al Bhed live? Bikanel Island (second answer down)
4) What is Al Bhed in Al Bhed? Al Bhed (first answer down)
You receive a Skill Sphere for successfully opening this chest.
Now go into the doorway on the far let side of the main room. Walk towards your team and you will be thrown into another battle against a Guado Guardian and two Chimaeras. Descend down the stairs after the battle to initiate a few more cutscenes.
Open up the treasure chest at the bottom of the stairs to receive a Lv. 2 Key Sphere. On the other side of the room is another treasure chest that is a little more hidden. Use the screenshot below to locate it and you will find a Lv. 4 Key Sphere. Go through the doorway to continue the story.
There is a treasure chest on the far left side of the room that contains 10,000 gil. Grab it and then head out the exit and follow the pathway along to board the airship.