Do you want to retire a millionaire? Answering the question is easy: Of course you do! But actually doing the work to achieve it through investing is something different entirely. If long-term growth is really on your mind, slow and steady is the way to go. Forget about finding the next GameStop or jumping on a day-trading bandwagon. Instead look for businesses that have had many years of strong growth and have more left down the line. If your stocks were to grow at an average annual rate of 15% over the next 25 years, investing a little over $30,000 today would be enough to reach the $1 million mark.

Attaining a 15% growth rate is by no means a given, but that's where being strategic and investing in high-growth areas like cannabis, sports betting, and tech can help you. And three stocks in those industries that are attractive buys right now are Cresco Labs (OTC:CRLBF)DraftKings (NASDAQ:DKNG), and Baidu (NASDAQ:BIDU)

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1. Cresco Labs

The cannabis industry is in its very early growth stages. Pot is legal for recreational use in just 16 states in the U.S. and remains illegal at the federal level. There are many markets out there that are still untapped. Chicago-based Cresco Labs knows all too well how quickly things can take off. In its home state of Illinois, the recreational pot market officially opened for business in January 2020. And during 2020, the state generated $1 billion in sales between its medical and recreational segments. To put that into perspective, in Canada, the entire country's adult-use sales totaled just $2 billion last year.

Cresco Labs makes for a great investment to take advantage of all that growth. The company has been achieving incredible sales numbers while posting a strong bottom line. On Nov. 18, 2020, Cresco released its most recent quarterly results for the period ending Sept. 30, 2020, in which sales of $153.3 million grew 62.6% from the previous quarter, and were more than four times the $36.2 million that the company reported in the prior-year period. Cresco also posted a positive net income of $4.9 million in its most recent results.

Since its business is in great shape, Cresco Labs is wasting no time expanding into new markets. On Feb. 1, it announced that it received the green light from the Arizona Department of Health Services to begin selling adult-use products in the state. Arizona marks the fifth state that Cresco is operational in where pot is legal for recreational use.

With plenty of growth still out there and the business already generating strong financial results, investing in Cresco today could pay off big over the long haul. Over the past 12 months, the pot stock is up 186%, wildly outperforming the S&P 500, which has risen by just 16% over the same time frame.

2. DraftKings

Another hot sector to invest in is sports betting. Unlike cannabis, sports betting is legal at the federal level, and it's up to individual states to decide whether they want to permit it. And many have -- more than two dozen states passed some form of legislation already.

All that growth has translated into some impressive numbers for the company. DraftKings last released its quarterly earnings on Nov. 13, 2020, in which it reported more than 1 million monthly unique payers on its platform for the period ending Sept. 30, 2020, up 64% year over year. Sales of $132.8 million were double what the company generated a year ago. That figure would put it at a run rate of only $530 million. And DraftKings is expecting much more growth, projecting revenue to reach between $750 million and $850 million for 2021.

The one negative is that it may take some time for the business to become profitable. DraftKings reported a loss of $347.8 million in its last quarter, which is more than six times the $55.9 million loss it incurred in the prior-year period. But with sales and marketing expenses of $203.3 million more than tripling from a year ago, DraftKings is investing heavily into promoting and growing its business, and that can make the losses easier to swallow for growth investors.

Keeping in mind that DraftKings is posting relatively strong growth numbers in an emerging industry and is courting big names (like Michael Jordan) to get involved with its business, this stock looks like it can be a winner for a long time. In the past year, its shares are already up more than 250%.

3. Baidu

To say that the tech sector is home to lots of growth-oriented stocks wouldn't be an especially hot take. I think that China-based internet company Baidu is one of a number of massive tech stocks that can still help your portfolio grow significantly in value given the market it operates in. Last year, the Chinese economy grew by 2.3% amid the coronavirus pandemic while other countries, including the U.S., struggled and watched GDP levels plummet.

Baidu is the lowest-performing stock on this list over the past 12 months, but with returns of 158%, any investor would be more than happy to take those gains. The Chinese company is comparable to Alphabet's Google. It offers similar services, including search, maps, cloud-based storage, news, and even autonomous driving. In January, California gave Baidu the go-ahead to test driverless vehicles in its state.

And despite a poor outlook for ad revenue in 2020, Baidu is coming off a strong performance in this past year. On Feb. 17, it released its year-end results in which the company reported sales of $16.4 billion for 2020, which was relatively unchanged from the previous year. Its adjusted EBITDA totaled $4.2 billion, growing by 49%.

The tech company has a diverse business with many ways that it can continue delivering strong results for its investors. And now that the Chinese economy could potentially leapfrog 56 countries in per capita income by 2025, it's a great market for growth investors to gain some exposure to. 

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.