14 Won't Join: Buggy Is A Coward Who Hates Luffy

Buggy does not mind taking advantage of Luffy's naïve personality, but he hates him none the less. Buggy has hated him ever since the Straw Hat captain defeated him in Orange Town.

Does Buggy reunite with his crew?

After the Summit War of Marineford, Buggy reunites with his old crew, and the two combined, greatly increasing the crew's status and power.

Does Buggy become a warlord?

70 Chapter 700 (p. 13) and Episode 629, It is revealed that Buggy has become a Warlord.