It might be easier to try to go a self-publishing route. I would suggest self-publishing online, selling ebooks, and then selling print copies at a local anime convention. It's very tough to get into Shounen Jump, especially if you don't live in Japan and can't write in Japanese. My main tip would be to think about what people might want to see in a shounen/action anime story that doesn't exist yet. I started this blog due to mainly wanting to write what didn't exist yet, in-depth critiques of anime. All I really found were shallow news articles about release dates that read like commercials, lacking in substantial information or critical discussion. So, with manga, fiction, nonfiction, or anything, write what you want to exist, that doesn't.