According to 80,
  1. Personal productivity
    Time management, task management, goal setting, etc.
  2. Science and math
    Especially applied math subjects like physics, statistics, and economics.
  3. Management
    Find a job that involves management, find a mentor, reflect on your mistakes, read a lot of books.
  4. Persuasion and negotiation
    Work in sales, entrepreneurship and consulting.
  5. Computer Programming
    There are multiple boot camps that provide accelerated three month training courses.
  6. Entrepreneurship and leadership
    How to Start a Startup YouTube channel. Improve as a manager and communicator. Work your way toward leadership positions. Set up and run your own project, society, or company.
  7. Communication skills
    Speaking, writing, listening and general social skills. Improve these skills through practice, reflection, and mentorship. Work in journalism, sales & marketing, and politics.