Well, starting a Luann comic strip fan fiction requires a good understanding of the source material. Read as many Luann comics as you can. Once you have a feel for it, think about what aspect of Luann's world you want to explore. Are you interested in her relationships, her hobbies, or something else? Then, start jotting down ideas for characters, settings, and events. You can also look at other fan fictions for inspiration, but make sure to put your own spin on it. Start small, with a short story perhaps, and then gradually build up your skills and confidence to write more complex fan fictions.
One interesting Luann comic strip fan fiction could be about Luann's future career. Maybe she becomes a famous artist and travels the world for inspiration. Another could be a story where Luann has a mystery to solve in her school. There are also fan fictions that focus on her relationships, like a deeper exploration of her friendship with her best friend.
I'm not familiar with Bets in the Luann comic being described as 'black'. It's possible it depends on specific storylines or character traits within the comic. Do you have more details to share?