One Piece Story is the detailed journey of Monkey D. Luffy from the start. The Ultimate goal for Luffy is to be the King of Pirates. The Captain of Straw Hat pirates started his journey from a small island called Foosha Island. He was an orphan not knowing his parents and brought up by his grandfather, Garp. Now, he is at the Wano Country taking down a Yonko. The One Piece Timeline is confusing when trying to explain the ages but let us break it down to different periods.
At Foosha Island
The prologue of the anime when Luffy first ate his devil fruit and was saved by Shanks. At this young age, he was very impressed by the power of the Pirates inspiring him to set sail and find the treasure, One Piece. Luffy meets Ace and Sabo who become his brothers, in the same age. Luffy was fourteen when Ace started his journey to the sea.
Started his Journey
Luffy had a deal with his brothers, that they will all set sail and become pirates after the age of seventeen. This was the Luffy that we saw in the first episode of One Piece. He is trained to fight with basic opponents using the force produced by his devil fruit power of rubber.
Straw Hat Crew
Zoro: He joined the crew first after Luffy saved him from a Marine HQ. Zoro is a skilled swordsman.
Nami: She was a thief. Luffy saved her village from some Fishmen. She is the crew’s navigator.
Usopp: He is a sharpshooter who joined the crew after his village was saved by Straw Hats.
Sanji: Luffy wanted a cook for his ship so he recruited the best chef from the floating restaurant, Baratie. Sanji can skillfully fight with his legs.
Chopper: He is a reindeer who turned human after eating a devil fruit. Chopper is the doctor of the crew.
Robin: She was a former enemy that decided to join Luffy’s crew because of his charm. Apparently!
Franky: He is a cyborg carpenter who made the new ship for straw hat crew and joined them.
Brook: He is a skilled musician and swordsman who joined the crew to sail with them to the end of the Grand Line.
There was a time skip after the Sabaody Arc when the crew fell apart and trained for 2 years separately. The whole crew including Luffy became stronger and matured over this time.
Jinbe: He joined the crew after Luffy asked him to join after the time-skip. Jinbe is a former Warlord.
Luffy is still aged 19 in the Wano Country Arc. The age problem was discussed by the writer of One Piece, Eiichiro Oda in a recent volume. He explained that even though the story is long, the events are continuous.
It is funny that the Manga is in its 23rd year running but Luffy has only aged two years since the first chapter. Luffy was seventeen in the whole pre-time-skip era. These arcs were less than a year in the One Piece World.
Later, The crew got separated at Sabaody. When Luffy returned from the two-year training, he was now 19 years old. There is still no update on that age even though many arcs have passed. Even if it seems like a lot of time has passed between the arc, Luffy is still a teenager. Since the time-skip, there have been fewer arcs than before the time-skip that is why there is less change in his appearance. Oda maintains that a few months have passed after the time-skip. It was speculated that Luffy will reach age 20 when he reaches the Wano Country.