One Piece — Filler vs Canon Guide
East Blue Saga (Canon Arcs)
Core origin of the Straw Hats: Romance Dawn, Orange Town, Baratie, and Arlong Park.
Warship Island Arc
Dragonite story. Can safely skip before entering the Grand Line.
Alabasta Saga (Loguetown to Arabasta)
Vivi, Crocodile, Baroque Works, and the true scale of the Grand Line.
Post-Alabasta & Goat Island
Episodic filler stories for each crew member. Safe to skip.
Skypiea Saga (Jaya & Sky Island)
Mont Blanc Noland, Enel, the Golden Belfry Bell, and major void century lore.
G-8 Marine Base Arc (Navarone)
Filler Hall of Fame! Widely celebrated as the best filler arc in anime history (Vice Admiral Jonathan vs Straw Hats).
Water 7 & Enies Lobby Arc
Peak emotional storytelling: Robin's backstory, Gear 2, and declaring war on the World Government.
Marineford War Arc
Whitebeard Pirates assault Marineford to save Portgas D. Ace. Essential turning point.
Dressrosa & Whole Cake Island
Doflamingo, Gear 4, Big Mom tea party, and Katakuri mirror duel.
Wano Country & Egghead
Gear 5 awakening, Kaido battle, and the beginning of the Final Saga.