-rep beats his meat as a hobby

.⠄⠄⣿⣿⣿⣿⠘⡿⢛⣿⣿⣿⣿⣿⣧⢻⣿⣿⠃⠸⣿⣿⣿⠄⠄⠄⠄⠄
⠄⠄⣿⣿⣿⣿⢀⠼⣛⣛⣭⢭⣟⣛⣛⣛⠿⠿⢆⡠⢿⣿⣿⠄⠄⠄⠄⠄
⠄⠄⠸⣿⣿⢣⢶⣟⣿⣖⣿⣷⣻⣮⡿⣽⣿⣻⣖⣶⣤⣭⡉⠄⠄⠄⠄⠄
⠄⠄⠄⢹⠣⣛⣣⣭⣭⣭⣁⡛⠻⢽⣿⣿⣿⣿⢻⣿⣿⣿⣽⡧⡄⠄⠄⠄
⠄⠄⠄⠄⣼⣿⣿⣿⣿⣿⣿⣿⣿⣶⣌⡛⢿⣽⢘⣿⣷⣿⡻⠏⣛⣀⠄⠄
⠄⠄⠄⣼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⠙⡅⣿⠚⣡⣴⣿⣿⣿⡆⠄
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⠄⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⠑⣿⣮⣝⣛⠿⠿⣿⣿⣿⣿⠄
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5. On the second floor, just past the currently closed door of the Accessory Shop's upper level, there is a row of sliding cabinets. Jump over and unlock the blue chest for another Post Card. Mail it to receive a mythril shard.
6. In 3rd District, behind the fountain up the ramp, there is a blue trinity that will give munny and a camping set.
7. You can unlock a door in the 3rd District to return to the 1st District for faster travel later.
Note: You can do these first 3 worlds in any order you choose. My recommendation is to do Wonderland first, then Deep Jungle even though the Coliseum is a lower battle level than Deep Jungle. This is because the Coliseum is really just fighting bosses and waves of heartless so it makes it a lot easier to get through with the least frustration.

Note: There are a few tasks that can be done before leaving:
1. There is a blue trinity on the ground just in front of the Cafe Bar in the 1st District. Walk toward it to trigger the walkthrough/tutorial. It will take you to the second level where you can open a chest that contains a post card.
2. Use the mailbox on the same level as the Cafe Bar to mail the post card you obtain from the blue trinity to receive a tent.
3. Speak to Leon in the Cafe Bar to activate the 101 Dalmatians side quest.
4. There is a blue trinity near the gate leading to the gummy ship in the 1st District which contains munny.

BOSS: Guard Armor
HP 700 EXP 110
This Heartless has 4 body parts, and a torso. Each one can be locked on to and attacked separately. It's a good idea to take out the limbs first. Hit it with a few combos and then move out of the way. It has a spinning attack, which can be stopped if you attack it at the right time. It can also throw itself at you. This does critical damage. So jump away when it launches itself towards you.

Donald and Goofy are added to your party.

Now you can make your way to the Gummi Ship by exiting the World from the 1st District after learning the Blue Trinity. From the Overworld Menu plot your destination for the world with the 1 star battle rating.

Leon
HP 135 EXP 30
Believe it or not, it is possible to beat Leon. However, it doesn't matter if you lose.

You'll wake up in Leon and Yuffie's room. Talk to Leon and then open the treasure chest. Talk to him again to get a cutscene.

Go to the second district. The door should be right next to you. Now go straight and take the first right. There should be a door that leads to the third district. Here, you will be paired up with Donald and Goofy. After defeating the first wave of Heartless, you will come face to face with Guard Armor.