Luffy learned to use Kenbunshoku Haki during the two-year timeskip. With it, he is capable of sensing the presence of others and greatly aiding his reflexes to dodge attacks such as bullets.
While in Totto Land, he strengthened this Haki by battling Charlotte Katakuri, who had mastered this Haki enough to enable him to see a little bit into the future.
Luffy can now see the future as fluidly as Katakuri, as shown when he helped Hyogoro dodge multiple attacks from Alpacaman and Madilloman before they happened.
Luffy learned also to use Busoshoku Haki during the two-year timeskip.
Luffy has advanced his Busoshoku Haki, allowing him to project it from his palm as well as progress even further by destroying objects he touches from the inside.
After training for a week under Hyogoro, Luffy now appears to be able to project his Busoshoku Haki at will, as seen when he was able to blast a hole through a tree by projecting from his fist. It is unknown if he is capable of destroying objects from the inside at will.
Luffy possesses Haoshoku Haki, a very rare type of Haki whose users are said to have the qualities of a king. This power was latent within him.
Silvers Rayleigh taught him about this power on Rusukaina, and Luffy trained to use it at will. At Fish-Man Island he was able to knock out 50,000 members of the New Fish-Man Pirates in an instant.
When he fought against fellow Haoshoku Haki users Chinjao, Donquixote Doflamingo, and Charlotte Katakuri, their clashes created a notable effect similar to lightning.
Luffy’s Haoshoku Haki is continuing to improve during Wano arc.