What is Luffy's "first gear, second gear and third gear"?

There is no such thing. In fact, the so-called first gear is the ordinary state of Luffy.

The second gear will emit white gas, which is very fast, but the second gear will cause harm to the body, the body will emit steam, and the skin will turn red, just like using stimulants.

The third gear is to increase the damage through the attacker's own size. Similarly, the elasticity of rubber is used to make the arm huge, and the air enters the bone by biting the finger and blowing, which greatly expands the body. You can only use rubber, and the side effect is that it will be humanized after the battle.

The ability in One Piece is mainly divided into body art department and ability department.

One piece has no so-called magic concept, and Dragon Ball has no so-called million-dollar gas bomb. The ability set in OP makes its battle scene very straightforward. From fist to flesh, all kinds of demon fruit abilities enrich the battle scene, but it also sets the armed color domineering restraint ability cultivated by pirates in the second half of the Grand Trace, which is a contest between the body performer and the demon fruit ability, and the demon fruit ability usually has both body skills. However, it is estimated that the domineering restraint of this natural ability is also added to balance the ability and body when creating. In the first half, Luffy really ran when he met the natural ability. In the first half of the grand line, the natural ability is almost invincible.