Appearance
He is often seen in a long green cloak and recently he wears the clothes of a revolutionary. He has, what resembles, tribal tattoos on the left side of his face and spiky black hair with a widow's peak hairstyle. He is almost always seen with a sinister smile on his face.
Personality
His personality is mostly unknown due to the many mysteries surrounding him, save for an apparent love for freedom and belief in fate, which are traits of a D. Unlike other members of his family, or D's for that matter, he looks stern and serious, though in all his appearances so far, he wears a smug grin. He speaks as though he is a mystic of sorts. He didn't like to speak or be asked about his past. He also has a strange habit to always look toward East Blue when he is "feeling" the wind. His revolutionary comrade Emporio Ivankov attributes this to his instincts, having left Luffy in East Blue. Iva also says that Luffy's will to live and his phenomenal strength only help solidify the idea that he is Dragon's son, implying that Dragon has similar willpower and strength.
Enemies
Due to the fact that he is the leader and main center of the largest anti-government organization in the world he has been dubbed the most dangerous and wanted man by the World Government. As stated by Robin many people and organizations (especially pirates) would try to steer clear of disrupting the World Government and drawing attention to themselves, although the organization which is lead by Monkey D. Dragon does the exact opposite. Although many people call him a revolutionary the World Government feels that his ideals and goals can collapse the strength and justice which is known as the World Government. So far it seems the World Government is the only known enemy of Dragon.
Abilities and Powers
Little has been revealed about Monkey D. Dragon's abilities; however, he is the leader of the Revolutionaries and has full command of the organization.
Emporio Ivankov also noted that the World Government's decision to capture Ace will prove problematic to them as they'll have to deal with both him and Whitebeard. This would imply that Dragon himself is a very powerful person. Also, as Ivankov has stated that Luffy's strength, willpower, and presence are just like Dragon's, it can be implied that Dragon possesses just as much super-human attributes, more or less.
He does appear to have some kind of affinity to weather as it is heavily implied he started the tornado and lightning storm in Loguetown and has been said to "feel" the wind. Also, the color of the wind at Loguetown that Dragon used was a greenish color which further strengthens the implication that he could have a Devil Fruit power.
Past Story
Dragon's history remains mostly a mystery, thus it is unclear why Luffy was left to be brought up by his grandfather Garp instead of himself. At some point he began the Revolutionary movement becoming its leader and his ideals began to slowly spread throughout the world. One by one countries slowly began to support him, though sometimes through war.
The little known history on him is that six years ago, in the Council of the Kings in Mariejois, the purpose was to discuss his revolutionary movement and his ideals that were threatening the World Government. Thalassa Lucas showed the picture of him. It was then he revealed that Dragon was currently no real threat, but would become so, in 5-6 years or so, if not dealt with.