One Piece is a big commitment, and the first arcs look dated next to modern anime. Stick with it. Luffy’s dream of becoming King of the Pirates sounds simple, but the world grows into one of the most detailed and inventive in fiction.
What keeps people watching for years is the crew. Each member has a past and a dream, and the arcs that focus on them are some of the most emotional in anime. The humor is goofy, the villains are wild, and the payoffs are earned over hundreds of episodes.
Start from episode 1 and go at your own pace. The films are optional extras.

