Are you a Robinhood investor or plan to be one? The hot mobile trading app registered 3 million new users in just the first quarter of 2020, and some of them have been making a lot of money since the market has recovered from the shellacking stocks got in March.

In August, Robinhood users were scooping up shares of Moderna, Eastman Kodak, and Nio. That's a mighty aggressive list of names that have one thing in common: high risk. Will Moderna's vaccine be successful, can Eastman Kodak win by entering an entirely new field, and will Nio resolve investors' concerns about its balance sheet?

While these companies are impressive in their own right, buying them all would create a portfolio of maximum risk, which can be a bit unsettling, even to younger investors with a long-term horizon. But Robinhood also offers a way to avoid this by diversifying your portfolio with exchange-traded funds, or ETFs.

The letters ETF on piles of coins.

Image source: Getty Images.

Robinhood offers roughly 500 ETFs to purchase. Here are three top buys that can help make you a successful investor while limiting destruction of your portfolio if one company takes a hit.

A safer way to invest in AI and robotics

According to Fortune Business Insights, "The global artificial intelligence (AI) market size was valued at USD 27.23 billion in 2019 and is projected to reach USD 266.92 billion by 2027," which translates to a compound annual growth rate of 33.2%. Currently, robots are performing surgeries and cleaning our floors, and they'll be able to perform many more tasks as the technology develops.

But how does an investor decide which company is going to be the leader and which may fall by the wayside? With the Global X Robotics & Artificial ETF (NASDAQ:BOTZ), you don't need the answer.

BOTZ invests in companies that "potentially stand to benefit from increased adoption and utilization of robotics and artificial intelligence (AI), including those involved with industrial robotics and automation, non-industrial robots, and autonomous vehicles."

It currently has 31 holdings, including NVIDIA Corp, Intuitive Surgical, and Brooks Automation, that span more than seven countries. BOTZ invests at least 80% in companies in the Indxx Global Robotics & Artificial Intelligence Thematic Index.

If you want a high-growth opportunity in a high-risk business with some safety added, this is a perfect ETF to augment your stock portfolio.

Coins in bowl being scooped out by spoon with various currency underneath

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Little bites of lots of stocks

There are so many stocks available for purchase -- wouldn't it be nice to buy a little piece of them all? You can by purchasing an S&P 500 index fund. This can help soften the blow of a hit-or-miss strategy that you use when picking individual companies and will give your holdings a foundation while you're out there looking for the next Tesla.

Robinhood offers you the opportunity to invest in the the SPDR S&P Index Fund (NYSEMKT:SPY), which "tracks a market-cap-weighted index of U.S. large- and midcap stocks selected by the S&P Committee." And it even pays a dividend, with a dividend yield of 1.63%.

By adding an S&P index fund to your holdings, you'll have a portfolio foundation with a long-term average return of 10%. As a result, you'll be achieving a nice growth rate while you're out there shooting for the moon with individual stocks.

Calculator, model house, and book reading REIT on desk

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Add some real estate -- with a dividend

Finally, you have an opportunity to diversify your portfolio and add passive income with a dividend by investing in a real estate investment trust (REIT). A REIT gives investors the chance to invest in broad-based real estate without having to purchase it directly. Robinhood offers the Vanguard US REIT Fund (NYSEMKT:VNQ), which "tracks a market-cap-weighted index of companies involved in the ownership and operation of real estate in the United States."

This diversified fund holds REITs in healthcare, hotel and resorts, industrial properties, and residential, and has a dividend yield of 3.76%. Some of its top holdings include American Tower Corp., Public Storage, and Welltower.

The fund is a nice complement to a portfolio of mostly Robinhood growth stocks, as it won't necessarily move in tandem with individual securities.

It's sure nice to make a killing when a gem like Tesla rises seemingly to the moon, but you can't always find a diamond in the rough. Take advantage of what Robinhood has to offer by adding the above ETFs to your portfolio, and you'll minimize your risk through portfolio diversification. You can then have some financial stability as you set off to find the next million-dollar baby.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.