Australian fitness mogul Kayla Itsines has built an exercise empire over the past decade, amassing 15.6 million Instagram users tuning into her content. 

The influencer first tasted success with her 12-week “Bikini Body Guide” (BBG) fitness program—a business model she cofounded and bootstrapped, which launched her to self-made millionaire status at just 22 years old. The serial entrepreneur then rebranded the venture to a personal training platform Sweat App, which garnered an online community of 50 million members. And just six years later, Itsines sold Sweat to fitness platform iFIT for a whopping $400 million.

Many might expect entrepreneurs who sell their companies for millions to retire early and live entirely off the fortune from their sale. But Itsines isn’t one to rest on her laurels; instead of kicking back, the founder strategized how to make it last. She put money towards a whole host of promising ventures—and one unconventional investment has become so successful that even she’s surprised.

“The first thing that ever made me money that I was so excited that I bought was a petrol station,” Itsines recently revealed during an interview with The School of Hard Knocks. “And I was like, ‘Wow. Out of all the millions of dollars, it’s so cool to see rent coming in from a gas station.’”

For those wanting to replicate her financial success, Itsines’ advice is luckily a lot simpler than selling a $400 million company in your 20s. Instead of hedging all their bets on one major investment, people should fan out their wealth across different industries and enterprises, Itsines recommended. 

“Don’t put all your eggs in one basket,” Itsines continued. She advised that everyone should be “diversifying your wealth, because one day the internet might shut off and it will be gone.”

Fortune reached out to Sweat for comment.

Investing advice from CEOs: Put down the Birkin bag, and 

Itsines had the right idea when she followed her inkling to build a diverse asset portfolio early; other investing moguls, from prominent value investor Mohnish Pabrai to the “Oracle of Omaha” Warren Buffett, have echoed the same strategy. 95-year-old Buffett started amassing his eye-watering net worth when he was a young, scrappy entrepreneur—and he now sits atop a $143 billion fortune. 

“Start young,” Buffett said during an annual Berkshire Hathaway meeting in 1999. “We started building this little snowball on top of a very long hill…We started at a very early age in rolling the snowball down, and of course…the nature of compound interest is that it behaves like a snowball.”

Nasdaq CEO Adena Friedman also believes that aspiring investors should learn more about financial strategy by simply trying. Putting money towards stock for the first time may be daunting—but the executive says there are several ways for even the most risk-weary professionals to get their foot in the door. 

“Learn by doing—with small amounts of money, or even on platforms where you don’t actually have to use real money,” Friedman told CNBC Make It at the Fortune Global Forum in 2024. “As you get more engaged and more educated, you can start to take more risks…and then get more confidence.”

Other finance legends are warning budding investors of purchases that will swallow up their money. Peter Tuchman, an iconic NYSE floor trader and the “Einstein of Wall Street,” has witnessed what investments actually hold up after four decades of career experience navigating market crashes. He cautions against the idea that buying a rare watch or exclusive Hermès Birkin bag will lead to a big payoff down the line—instead, people should be putting their money towards the companies that create the products. 

“One of the most important things is to invest in stocks and not stuff,” Tuchman said in a video posted by The School of Hard Knocks last year. “Pretty much most things we buy goes down in value the minute you buy it.”