Berkshire Hathaway CEO Warren Buffett has been wildly successful for several decades, making him the world's 10th-richest person as of this writing.

He also has given his followers and shareholders priceless investment advice over the years. But when it comes to investment choices, only one truly counts.

The best investment

In an essay he wrote for Forbes in 2017, Buffett stated:

[Ultimately], there's one investment that supersedes all others: Invest in yourself. Address whatever you feel your weaknesses are, and do it now.

Simple, logical, yet counterintuitive. How many investors even consider this as a personal or business strategy? Unlike risky investments that can go poof! overnight, this one single investment choice can produce a lifetime of return. And, to Buffett's point, nobody can take away the knowledge and skills we amass over time. Buffett says,

Nobody can take away what you've got in yourself--and everybody has potential they haven't used yet. If you can increase your potential 10 percent, 20 percent, or 30 percent by enhancing your talents, they can't tax it away. Inflation can't take it from you. You have it the rest of your life.

Here are three great ways to invest in yourself and your personal development:

1. Your communication skills

In a video posted on LinkedIn, Buffett said,

If you can't communicate, it's like winking at a girl in the dark--nothing happens. You can have all the brainpower in the world, but you have to be able to transmit it. And the transmission is communication.

He added that investing in developing your communication skills -- both in writing and in-person -- "can increase your value by at least 50 percent."

2. Your leadership skills

Buffett has no shortage of advice about the importance of good management skills and finding integrity in leaders. He once asked University of Florida students to think of a classmate they felt had the makings of leadership success long term, such that they would want to get 10 percent of that person's earnings for the rest of their lives. Here's what he said:

You would probably pick the one you responded the best to, the one who has the leadership qualities, the one who is able to get other people to carry out their interests. That would be the person who is generous, honest, and who gave credit to other people for their own ideas.

3. Your professional relationships

One of the greatest gifts I've received is that of learning from a close group of mentors. Not only are these are sages further down the path than I am, but also I know I can trust their advice and wisdom because of their unquestionable character and interest in my own development. In The Snowball, a biography of Warren Buffett authored by Alice Schroeder, he drives home my point: "I learned that it pays to hang around with people better than you are because you will float upward a little bit. And if you hang around with people that behave worse than you, pretty soon you'll start sliding down the pole. It just works that way."