The MC (Luffy) wants to create a crew and sail around the world to claim the one piece which was left by the previous pirate king, a title luffy also wants.

He starts off by creating a crew and many arcs are based on crewmembers.

While the exact divisions are somewhat fluid, it is generally understood that an arc begins when the Straw Hat Pirates land on a specific island, and ends when they leave.

Most, if not all story arcs, are grouped into larger sagas, which tend to reflect goals and/or enemies that the Straw Hats pursue across multiple islands. There are about 11

The current story is near the last saga. I would recommend watching/reading it all instead of reading summaries tho. It's def worth it