This trophy will single-handedly force you to do at least three partial playthroughs of the game, as Cloud, Tifa and Aerith each have three possible dresses they can wear in Chapter 9, and what dress each character ends up wearing depends on what side quests they do in Chapter 3 (Tifa), Chapter 8 (Aerith) and Chapter 9 (Cloud).
For Tifa, you’ll need to complete all the side quests in Chapter 3, after which you’ll unlock the Alone at Last Discovery Event. Complete this event and you’ll get to choose between three hypothetical outfits: “Something mature”, “Something… sporty?” and “Something exotic?”. What you say will determine what Tifa wears in Chapter 9, and if you fail to complete all the side quests and/or this Discovery Event, Tifa will default to the “Mature” dress.
Aerith’s dress choice is fairly straight-forward as well, as it’s determined by how many side quests you complete in Chapter 8. If you do every side quest in chapter in chapter 8 she’ll end up wearing an elegant red dress, if you do some of the side quests in Chapter 8 (say, 3/6) she’ll end up wearing a dark pink dress, and if you do none of the side quests in Chapter 8 she’ll end up wearing a… rather ugly light pink dress.
Cloud’s dress is where things get complicated. There are five side quests in Chapter 9, and depending on some choices you make throughout that chapter you’ll get different quests from different characters (see Best in the Business for more details on how to unlock these quests). One quest, Burning Thighs is universal, but The Party Never Stops and A Dynamite Body are exclusive to Chocobo Sam, while The Price of Thievery and Shears’ Counterattack are exclusive to Madam M. The dress Cloud ends up wearing is determined by whether you do all of Chocobo Sam’s quests, all of Madam M’s quests, or none of the possible quests.
Make whatever choices you wish on your first playthrough (we suggest doing all the quests possible for the Divine Gratitude trophy, and Chocobo Sam’s quests for The Johnny Experience trophy), after which you’ll need to replay Chapters 3, 8 and 9 to get the other three. This trophy should pop late in Chapter 9, when you unlock Cloud’s third dress.