Ashton Kutcher says the best investment he's ever made is something anyone can afford

If the name Ashton Kutcher still brings to mind "Dude, Where's My Car," you're behind the times.

In the past few years, the actor turned entrepreneur and investor has cofounded a viral media siteand a human-rights organization,appeared on "Shark Tank," and invested in buzzy tech companies such as Spotify, Airbnb, Uber, andMeerkat.

In Grow, the new digital magazine from investing app Acorns(another of his investments), Kutcher talks about everything from why he got started investing to the best investment he's ever made — and it isn't a tech company.

When asked what he considers to be his best investment, Kutcher tells Grow:

My relationships — taking the time to get to know [people], what motivates them, what their challenges are. These things are often overlooked. Investors get so wrapped up in returns and numbers that they forget that the true privilege of their position is to share a journey with exceptional people.

Kutcher's reflection has a practical takeaway for just about anyone: The best investments don't have to cost a fortune. Investing in relationships can cost as little as a few cups of coffee and a handful of emails.

His advice to people wondering what they should invest in can be similarly affordable:

First: Yourself! Double down on your own expertise, your passion, the thing you do when you have free time.

[Then] pay attention. If you work in a grocery store, pay attention to the items that you can't keep in stock, and the new things that are hitting the shelf. If you are a contractor, investigate the new materials showing up on jobs. Who makes them? Why are they better? You may have a more educated opinion than you are giving yourself credit for. Too often, people speculate on investments based on what's making someone else rich and forget to do a deep index on their own behaviors.

Invest in that which you would like to see become a reality. Worst-case scenario, you lose money — but at least you will get the life you want.

If you're ready to invest, take a look at the online courses that can help you get rich and read up on why you should stop networking if you want to be successful.