who are the most important characters in the story?

Jim Hawkins, Billy Bones, Black Dog, Squire Trelawney, Dr. Livesey

For additional characters, please visit the gradesaver page linked below;

http://www.gradesaver.com/treasure-island/study-guide/character-list/

Jim Hawkins, Black Dog, Long John Silver, Squire Trelawney, Mr. Smolett, Ben Gunn(he wants cheese), Captain Flinn, Billy Bones...all i can think of right now :D