What do you learn about Dills character?

We learn that Dill's a very adventurous and imaginative young boy. Dill runs away from home because he isn't very happy there; he doesn't think he gets enough attention from his mother and new stepfather. Many children run away from home, but they tend not to wander quite as far as Dill. His journey from Mississippi to Alabama indicates someone who's restless and prepared to take big risks to try and change his life. Even most adults would think twice before doing this.
Dill also uses his vivid imagination to come up with exciting new games whenever he plays with Jem and Scout. It's Dill who invents the famous Boo Radley game where the children act out scenes from what they imagine is the Radleys' crazy home life. The most exciting part of the game for the children is when Boo—played by Jem—stabs his father—played by Dill. This is based on the urban legend that Boo once attacked his old man with a pair of scissors.