What’s the best for a beginner?
Something they love so much they will continue even when they know how bad they’ve been and how slowly they are getting better…
Personally, novels, especially fantasy novels, are what I love writing so much I do it even when I’m terrible. I integrate my love for anthropology and culture; fiction can absorb any academic interest. But I’m terrible with essays, articles; so I can’t really say anything about that.
No market is easy, all of them you need luck and a lot of talent to get in on, so do what you can to improve and persist. Just like with anything else.