There might be a mentor - like character in the 'dream jumper graphic novel'. This character could be an older person who also has some experience with dream jumping and helps the main character understand and control their abilities. There could also be an antagonist, perhaps someone who wants to misuse the power of dream jumping for their own evil purposes, like stealing secrets from people's dreams or causing chaos in the dream world.
Since it's a graphic novel, there could be a diverse set of characters. The main character, the dream jumper, is likely to be at the center. They might have friends in the real world who are initially unaware of their power. In the dream world, there could be magical beings such as dream guardians who either help or hinder the dream jumper's progress. There could also be other dream jumpers, some of whom may be on different sides, either supporting the main character's mission or trying to stop them for various reasons.
I don't know the main characters in 'dream jumper graphic novel' since I haven't read it. But it could have a young protagonist who is the dream jumper, maybe a teenager who is just discovering their powers.