There are four DLCs to play Final Fantasy 15and although they are optional, they both contribute to the overall story and appear in specific chapters. Each party member has a certain time in the game when they are separated from the others, and during that time each DLC is available.
Each of the DLCs provides a better insight into how and why the character's personality changes over time, and provides a unique gameplay experience as you learn to play as someone else. You are Noctis. This is the best time to play each DLC.

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When should you play each DLC in Final Fantasy 15
Each DLC takes place during a specific point in the story, although you can choose to play them at any time afterwards if you want to focus on Noctis' story for a while. . That being said, playing DLC before the story takes place will obviously lead to spoilers, especially with the latest DLC that will be included in this article.
Each DLC is about 3 to 4 hours long with boss battles and time trials after you complete the main story.
When will the Gladiolus division take place
After the events of Chapter 6, Gladiolus leaves the party and spends most of Chapter 7; during this time the Gladiolus Episode happened. You can choose to play this DLC either before or after he returns to the party, as long as you play it and beat the boss after he leaves the party.
When will Episode Ignis happen?
Episode Ignis occurs at the end of Chapter 9 after Noctis fights Leviathan and falls unconscious. Although he doesn't leave the party like Gladiolus does, the events of this DLC take place between Chapters 9 and 10, with Noctis waking up long after the events. with DLC so you can choose to play it at any time after beating Leviathan. .
When will Episode Prompto happen?
the The beginning of Episode Prompto takes place during Chapter 12 when Prompto is hit by a train. The action in the DLC continues until part 13 when he rejoins the group and should be played after he returns at the end of 13.
When does the Ardyn episode happen?
The events of this DLC take place years before the events of the game, but everything about Ardyn is left a mystery until the end of the game. That is Suggested you win the first game and learn all the surprises about Ardyn before learning about his backstory, because that would spoil some of the surprises that are often discussed in the DLC.