If playing in the recommended order, Aqua's Land of Departure should be the final one. After the introductory scenes, Aqua is placed in a battle against orbs of light with a party of Ventus and Terra. This battle should be cleared without any trouble on all difficulties. It helps that Aqua is the most balanced Keyblade wielder of the trio; whereas Terra has an emphasis on power and Ventus an emphasis on speed, Aqua can dispatch enemies with great speed and powerful Magic all while having a 360° guard in the form of Barrier. If the orbs distance themselves from Aqua, use Blizzard. Otherwise, they can be taken care of entirely with physical attacks.
For clearing the battle, Aqua obtains her first Command Style, Spellweaver, which is entered via Magic Commands. After the scenes, Aqua obtains the ability to play Command Board, with the first map now becoming available, and forges D-Links with Ventus and Terra. She also gains access to the World Map with the use of her Keyblade Glider. While the following three worlds can be visited in any order, this guide orders them based on battle level.
After clearing the first world, Aqua can revisit the Land of Departure to collect some treasure. Land at the Summit to find a chest containing a Fleeting Crystal on the edge of a cliff, then exit to the Mountain Path. Two chests on the upper level contain a Shimmering Crystal and a Hi-Potion, while one on the lower level contains Bind.