A lot of people have come to realise the importance of skill, not just any skill, but skills that are marketable and of high demand. Most of these skills can be marketed online and clients can be earned online too.
Some good high demand skills include graphic designing, search engine optimization, programming, coding, website designing, editing, UX design, cloud computing, artificial intelligence, web development, digital marketing, etc.
These days, employers look out for specific skills. For example, if you are a writer, an employee would want to know if you're seasoned at SEO and SEM.
If you intend acquiring skills that would enable you earn big online, then go for on-demand skills, skills that can make you stand out even in a competitive sphere.