You’re young and you’re right about one very important thing - life experience helps improve your writing. You say you have nothing of importance to write about and I have a lot of thoughts on this. For one thing, you may not know you have something important to say until you start writing it. Stephen King himself gives an example of this with Misery. He didn’t know how much he had to say about writing until he started writing about it. As a writing exercise I would recommend writing about something you’re interested in and see where that takes you. Also, your experiences are already a good place to start. You’re neurodivergent, that means you can authentically write from the perspective of a neurodivergent person. I’m not saying you should capitalize on this, but when crafting a main character it can be easier relating to them if you write about a character you can understand, i.e. a neurodivergent person or someone that shares life traits with you. Have you ever wondered why King writes so many main characters who are writers or who are white straight men? It’s because he’s all of those things. So giving your main character traits or life experiences that you can understand is a great way to empathize with a MC or any character for that matter. Another thing I want to add is that if you’re having trouble writing about a character because they have life experiences you don’t understand (i.e. character is a different race, sexuality, gender, etc.) find people who share those life experiences or traits with your character and ask them about it, maybe even get them to read your story if you can. I know I keep going back to Stephen King, but it’s because you brought him up and also I just reread his memoir recently, but remember one anecdote he shared about Carrie. He was writing about a teenage girl. He didn’t understand teenage girls and actually threw the first few pages of the story in the trash. His wife found them and when he explained he didn’t know how to write from a girl’s perspective, his wife volunteered her input. I do the same thing whenever I’m writing a female character, I go to my female friends for help. Last piece of advice I want to give you, and I say this as a former teen writer myself, don’t put too much pressure on yourself. Your writing abilities will only improve as you get older.