Items: Postcard x6, Cottage, Camping Set, Mythril Shard x3, Mythril x2, Potion x2, Mega Potion x3, Mega Ether x2, Pretty Stone x2, Elixer x3, 100 munny
Accessories: Brave Warrior
Pluto wakes Sora up and then runs off. In this world you'll start in an alley. From here you can enter the main area of the First District. You'll see people from various worlds here, whose home worlds were also attacked by heartless. Lets explore the area a bit. Lets go to the item shop. Its on the right as soon as you come out of the alley. When you get inside you'll see Donald's nephews, Huey, Duey, and Louie. You don't really have any munny right now though. Instead jump on the counter and target the fan by hitting the R1 buttun. Jump and strike it to get a postcard. Head to the mailbox (its the red thing with the tounge sticcking out) and mail in the postcard. You'll get a cottage for mailing it. Getting more postcards means more items. Take a look at the postcards section for more info on these. Keep in mind you won't be able to collect them all just yet. I suggest coming back to get all of them after you've gotten all of your abilities.
Now head on into the Accessory Shop, right next to where you came out of the alley on the left. Here you'll find a save point, so save if you wish. You'll also meet Cid and afterwards you'll go on a hunt for Kairi and Riku.
Anyway head through the large double doors in the area up the stairs beside the Accessory Shop and you'll encounter the Shadow Heartless again. Wander around the area entering all the doors you can and you'll see Disney stars Donald and Goofy almost every time you do. Once you've gone through every door in the Second District head back to the Accessory Shop and talk to Cid. Save then leave the shop to encounter Leon (take a guess at who he really is).
After this you'll go through some scenes chock full of story goodness. When you can, talk to Yuffie and open the chest on the table to get an Elixir. Talk to Leon again. After the scenes you'll have to fight your way through the Heartless to the Third District. Before you go to the third district, I suggest heading back to the First District. In front of the Accessory Shop you should see Aerith. Talk to her for a Mega-Potion. Now go level up to about 10 or 12 and then head on to the third district. There you'll meet Donald and Goofy as a team you'll face some Heartless and then a boss.
Back in the First District, Leon will give you 100 munny and an Elixir if you beat him during your first encounter. Lets walk over toward the cafe. You should see a blue mark on the ground. Thats a trinity mark. They allow you to get items and access certain areas, but only when Goofy and Donald are in your party. Anyway, when you're at a trinity mark, choose the trinity command at the bottom of the command window. Go to the Trinity page for information where all of the trinities are.
With all that done head to the World Exit doors (the really, really tall ones in the First District) and head to the next World on Donald and Goofy's Gummi Ship, check the Gummi section for more details. Although you'll get a "nice" tutorial anyway. When you exit the world choose to go to the place with a Battle Level of 1. You really wanna do this.
Now that we're in our Gummi Ship, just shoot the other ships and collect the items they drop. Pressing the X buttons shoots and pressing the Circle button to slow down. I suggest you slow down in order to make it easier to get the items.