There are a lot of ways to define a no-brainer buy, but one I like is as follows: a company with a very promising growth story unfolding right now, trading for a bargain price. You can scoop up shares of such a player, and if the story goes according to plan, win big over time. At the same time, since these particular stocks are pretty cheap, you can get in on them with a small investment. That minimizes your risk.

Today, you can buy three high-potential stocks across three industries -- travel, e-commerce, and healthcare -- with just $50. They each have dropped in the double digits over the past three months, offering investors a deal on what may become winning stocks of the future. Let's take a look at these stocks to buy with $50 right now without hesitation.

1. Carnival

Carnival (CCL -0.66%) (CUK -0.88%) struggled during the early days of the pandemic as the crisis anchored its ships, and it built up a wall of debt. But the world's biggest cruise operator is proving it has what it takes to make it through the toughest of times and succeed over the long haul.

Demand for the company's cruises has taken off, and that's reflected in recent earnings reports. For example, in the fiscal third quarter, Carnival said total customer deposits reached a Q3 record of more than $6 billion, and the company's revenue hit an all-time high.

Even better, Carnival has offered investors some insight into how it plans to pay down its debt. The company has cut debt by almost $4 billion from its peak earlier in the year and says it expects its ongoing growth in adjusted free cash flow to keep chipping away at the rest. The company also aims to boost cash flow by becoming more efficient, with efforts such as replacing old ships with newer ones that don't use as much fuel.

Today, you can pick up a Carnival share for about $11, which leaves the stock trading at near-record lows in relation to sales.

CCL PS Ratio Chart

CCL PS Ratio data by YCharts.

2. Chewy

Chewy (CHWY 2.99%) is your pet's best friend, and the e-commerce company may be your best friend too because it saves you a lot of time. You can find everything from food to supplies and even pet insurance on Chewy. And pet lovers especially like the company's Autoship service, which automatically reorders and delivers the products they use regularly right to their door.

In fact, Autoship sales made up 75% of Chewy's total sales in the most recent quarter. This is positive because it shows most of Chewy's sales come from regular customers, offering a certain amount of visibility on future revenue.

Chewy just last year reached a big milestone: profitability. And the company continues to report growth even in today's difficult economic environment. In the most recent quarter, net sales increased in the double digits, and net sales per active customer also climbed in the double digits.

What's next for Chewy? The company just expanded into Canada, a market it says could reach the profitability and market share of the U.S. business. So this could be a big growth driver for Chewy in the years to come.

Meanwhile, Chewy's stock has dropped to about $18, leaving it at a record low in relation to forward-earnings estimates.

CHWY PE Ratio (Forward) Chart

CHWY PE Ratio (Forward) data by YCharts.

3. Ginkgo Bioworks

Ginkgo Bioworks (DNA 10.60%) is a company that specializes in organisms, and this could be a major business well into the future as these specially engineered organisms help pharmaceutical clients along the drug-discovery path.

Most recently, Ginkgo scored a research and development deal with big pharmaceutical company Pfizer that could be worth more than $330 million. It covers the development of mRNA drugs. And the company has signed deals with several other pharma and biotech companies. In fact, pharma and biotech made up 31% of Ginkgo's active programs in Q2; that's up from 18% about two years ago.

The company also works in the area of biosecurity, and though revenue here has fluctuated -- for example, peaking in times of insecurity such as earlier pandemic days -- Ginkgo aims to make biosecurity a recurrent revenue business. The company plans on doing this by focusing on the development of biosecurity infrastructure worldwide.

Ginkgo isn't yet profitable, but the company does have $1.1 billion in cash that it says should help it progress toward its goals. Considering Ginkgo trades for about $1.35 a share right now, the stock is a no-brainer buy for any growth portfolio.