In his pirate captain attire, he dons a striped white and red shirt with short sleeves, white gloves reminiscent of the ones worn by clowns, a sash around his waist like many other pirates, and a pair of loose pants reaching to his calves, just above a pair of striped socks and pointy shoes. He also has a scarf around his neck. Hanging from his shoulders there is an orange, fur-lined captain's coat. On his head he has an orange hat with his jolly roger on it, over a bandanna with the same pattern of his shirt. While in the manga his scarf and sash are orange just like many other components of his attire, his pants are light-brown and the epaulets of his coat are simply gold, in the anime he was given a much more bright color scheme, with a purple scarf, green sash, light-green pants, and green epaulets.
During the Whitebeard War Saga, after escaping from Impel Down, Buggy modified his striped prisoner's outfit with salvaged Marine uniform pieces to recreate the effects of a pirate captain: a coat and a tricorn that had the symbols crossed out.
As a young man serving aboard Gol D. Roger's ship, he looked mostly the same; the only notable differences were his shorter hair and smaller stature. He wore a different outfit in each flashback but dressed similarly to how he does now, usually seen in striped T-shirts (or collared shirts), white gloves, baggy pants, pointed shoes, and donning a sash. He wore beanies rather than a captain's hat and he lacked the captain's coat.
It was revealed in an SBS question that the blue tassels coming from the sides of Buggy's hat are his actual hair in the shape of two ponytails. While in the confines of Impel Down, Buggy's long hair is tied into just one ponytail.
After the timeskip, Buggy's appearance has changed greatly. His hair is not tied anymore and now looks spikier. He wears a big red and white, stripped tricorn with a rim ornated with several golden little balls and his crew's Jolly Roger on the front. He wears a big, red cloak, using his Devil Fruit powers to make himself appear larger.
Buggy will often feign intelligence, only to have his true incompetence revealed. Although he is not "stupid" in the traditional sense, he is prone to gross misjudgments that cost him; usually this is due to his overconfidence. In the original Japanese version of One Piece, he inserts "hade ni" (派手に hade ni?, literally meaning "flashy"), into almost every sentence he speaks ("Flashily die! You flashy bastard!").
His big red nose is something he is very touchy about, going so far as to destroy an entire town when a couple of kids made fun of his nose. Occasionally, he will mishear what others say as an insult about him or his nose, possibly due to paranoia.
He has a number of running gags in the series, including a delayed reaction towards things, he will at first act casually then when it sinks in he will act completely the opposite (for example, when Ace appeared on his ship, Buggy first greets him politely. Then, when he realizes he is on his ship, he blurts out "Who the hell are you?"). Sometimes he will even do the opposite of this and overact the part then become calm having thought the situation through more deeply after the initial reaction. He also has what some might consider "dumb luck"; no matter what happens to him he is lucky enough to survive somehow (including being struck by lightning at Loguetown, being chased by Smoker, being frozen alive by Admiral Aokiji, or inadvertently slashed by Dracule Mihawk).
Furthermore, through his crazy streaks of good fortune, coupled with weaselly actions and lying, he has managed to gain power and favor with people by doing next to nothing. Oftentimes, happenstance makes him look more impressive and intimidating than he really is; Buggy won't even intend to look good and have impressed people unintentionally or by total accident, or pass himself off as a substantial figure by being dishonest or stealing the credit for a masterful feat from someone else. Though he once tried to keep it a secret so he wouldn't become a target for rival pirates and the Marines, he also started playing up the fact he was originally one of the legendary Roger Pirates (despite being just an apprentice) once the truth was out.
These kinds of misunderstandings caused a large number of Impel Down escapees to join his crew (though Buggy did not intend to impress them during his jailbreak and only continued out of fear the prisoners, who were much more vicious and infamous than he was, would turn on him if he appeared weak) and Buggy to be selected to become a Shichibukai by the World Government just because he looked reputable from their point of view, though Galdino is well aware of Buggy's true nature of cowardice and ineptitude. After the timeskip, he has even stooped to making himself look bigger and more intimidating as a Shichibukai by splitting up his body underneath a cloak and growing out his hair.
Buggy is one of the few villains to become reformed after facing Luffy, though only slightly. He also begins to accept people's kindness, though he can still be cruel to anyone who is not a member of his crew or is aiding him in his goals. He also is fun loving and displays a huge fondness for parties, admiring those who are equally fun loving (strangely, he shares this trait with Shanks). He takes great joy in riding on the beliefs of others and took a great advantage of the cheering crowds of prisoners from Impel Down upon his escape, who were impressed with his history on Roger's crew, as well as his connections with Shanks. Strangly enough he breeds extreme loyalty in his his crew as the Impel Down prisoners all joined his crew and are all completely loyal to him increasing his strength to that of the other warlords.
He also has a strong love of treasure. Unfortunately for him, his obsession with treasure led to him leaving himself open in his first encounter with Luffy to attack Nami (who was attempting to take off with said treasure) and was just the small window the superior Luffy needed to defeat him. Buggy fails to understand how anything but gold, silver or jewels can be considered "treasure"; an opinion which apparently has not changed in over 22 years even though so far it has led to constant failure.
His primary goal is to get revenge against Luffy, for defeating him, and Shanks, for ruining his dreams during his youth. His dream is to become Pirate King and own all the treasures in the world. After the escape from Impel Down, with the encouragement of his followers, he put his sights on defeating Whitebeard and conquering the "top". Many of those he has known previously such as Luffy and Whitebeard see him as little threat.
Another strange trait of Buggy's is his complete lack of fear toward swordsmen, no matter how powerful they may be, in contrast to his cowardice against any other people stronger than him. This can be seen in such instances as his fight against Roronoa Zoro and Mihawk. This most likely is a trait he habitually developed because of his Devil Fruit-based immunity to cutting and slicing attacks. This is somewhat justified as no swordsman no matter how strong can ever kill him (although, if they fight seriously and can utilize haki they can bypass his Devil-Fruit immunities).
While not as powerful as other former Roger pirates, Buggy is a fairly capable fighter who was strong enough to survive all the battles with the Whitebeard Pirates and the extreme dangers of the Grand Line. His arrogance and greed usually gets the best of him, preventing him from fighting at his fullest. His great craftiness makes him a dangerous opponent as he will always use trickery in a fight.
While he was a considerable opponent at the beginning of the series, he became a lesser threat as more powerful enemies showed up. Finally, in the Impel Down arc, the Baroque Works members commented how weak or how much of a coward Buggy actually is. However, he is still able to survive the ordeals people far more powerful than him (albeit with their help).
One of the factors that assist Buggy in his exploits at least during the escape and the Battle of Marineford, would be his extraordinary luck. His uncanny ability to read the mood, as well as his love of theatrics and saying lines at a precise moment to strengthen the morale of his "crew" helped him secure their loyalty in furthering his plans. In addition, due to their misconceptions of his selfish actions, i.e.: running away out of fear as something to do with the death of Whitebeard and their short term partnership, as well as catching Jinbe by accident but they believed that was his plan all along, many pirates become extremely loyal to him. Most of the times they were in tears from his "heroics". He is always keen on grafting himself to the most powerful people around and bending them to his will and is smart enough to come up with battle plans on the spot this combined with his leadership skills make him an at least moderatly capable captain.
Thus proven, perhaps Buggy's biggest weapon is his cunning when it comes to speeches, the ability to easily lie and convince those around him to follow his bidding, this way gathering a crew with great strength.
Despite (or perhaps because of) his achievements coming from sheer luck and misunderstandings, he was at least acknowledged by the World Government to be strong enough, either in strength or influence, to be a Shichibukai.
Buggy has very high endurance and resilience, since he survived an explosion from a redirected Muggy Ball, with hardly any resulting injuries, while a similar Muggy Ball severely injured Minotaurus, one of the Jailer Beasts in Impel Down. He also possesses quite a great deal of physical strength, as he was able to lift and choke one of his subordinates with just one hand, lifting a Blugori easily and slamming it into the floor (although it got up again with minimal injuries) and managed to sustain the weight of both Luffy and Jinbe while floating with the upper part of his body. According to Shanks, he was also a great swimmer and was proud of the fact, but this was said before he ate a Devil Fruit and lost his ability to swim.
Buggy accidentally consumed the Bara Bara no Mi, a Paramecia-class Devil Fruit which allows him to separate his body parts and control them independently of each other, but robbed him of the ability to swim, which, according to Shanks (back when the two were still cabin boys at Roger's ship), he was excellent at. The abilities gained from this fruit also make Buggy immune to slashing, cutting and cleaving attacks; any such attack just separates him into his component parts, allowing him to reform as needed.
In addition, most of his body is capable of flying through the air, with enough force to send a man flying through a wall - with the crucial exception of his feet having to stay grounded. Even though the parts are separate, Buggy can still feel what the part feels; e.g. when Luffy attacked Buggy, he separated his torso from his waist, only to find that Luffy was aiming for the crotch (needless to say, this left him with a rather painful result).
Also, when Buggy used Bara Bara Festival in an attempt to take down Nami, Luffy took one of the feet and tickled it, causing Buggy to break down in laughter. No matter how much of his body he separates, something also seems to act normal; e.g., his feet walking as normal while Buggy sends the rest of his body flying. Though Buggy is a decent fighter and his Devil Fruit power makes him difficult to hit, he was constantly leaving himself open in the latter half of his match for Luffy due to distractions, resulting in many careless mistakes.
A weakness of his fruit is that if a component part is restrained, he cannot use the component part, shown by Nami when she restrained a part of his body in their first fight with him. Because he is invulnerable to cutting attacks, he could be considered the natural enemy to even the most powerful swordsmen, as seen when he easily survived Mihawk's extremely powerful slashing ability.
There are two major weaknesses of his Devil Fruit. The first is that his feet act as an anchor and must remain on the ground even when the rest of his body is airborne. Secondly, despite feeling them at all times, Buggy may lose pieces of his body if they leave his visual range, though once he can see them again he can easily guide them back.