Nico Robin is the sixth member to become part of the Straw Hat Pirates in One Piece.
Jinbe is the ninth member to join the Straw Hat pirates as the Helmsman.
Brook is the eighth member to join the Straw Hat Pirates as the Musician in the One Piece anime.
Franky is the seventh member to join the crew as the Shipwright at the end of the Post-Enies Lobby arc.
Usopp is the third member to join the Straw Hat Pirates as the Sniper. He initially led the Usopp Pirates crew, but he joined Luffy’s crew at the end of the Syrup Village arc
Tony Tony Chopper is the fifth member to join the Straw Hat Pirates crew as the Doctor.
Sanji is the fourth member to join the Straw Hat pirates as the Cook at the end of the Baratie arc in One Piece.
Nami is the second member to join Luffy and the Straw Hat pirates as the Navigator during the Orange Town arc.
Roronoa Zoro was the first person to join Luffy’s crew as the Swordsman and became the second official member of the Straw Hat Pirates.
Luffy's personality can be described as childlike, in the sense that he tends to go to the extremes.