Should I focus on common or niche skills to get a job?

I can take a year off to learn new languages/skills. Will I have more success if I focus on rare languages or common ones?

I’m an American expat living in Asia. I work remotely as a web developer for an American company, but I want to quit and find a new job.

I am not the most attractive employee because I am 14 timezones from PST. Will learning a language like Elixir get me a new job faster than than a mass appeal one like Java?