Turning $500 into $1,000 is not difficult. You don't need to follow a complicated strategy or chase speculative meme stocks to accomplish this. All you need to do is buy and hold shares of a fast-growing company with plenty of opportunities for further expansion and be patient.

To give you some ideas, three Motley Fool contributors offered their favorite picks. Here's why they chose Five Below (FIVE -1.75%), CuriosityStream (CURI 6.90%), and Chegg (CHGG -3.83%).

A stock chart showing an upward trending price.

Image source: Getty Images.

Five Below is the real deal

John Ballard (Five Below): Before the pandemic, Five Below was growing sales and earnings per share by over 20% per year, and so far this year, it's starting to pick up where it left off. In the fiscal first quarter, sales were up 64% over the same quarter two years ago. The stock has delivered market-smashing returns to investors over the last five years, up 367%, but Five Below still has plenty of opportunity to open more stores and deliver above-average returns to investors.

The store count stood at 1,087 across 39 states at the end of the fiscal first quarter, but management still sees potential for over 2,500 stores over the long term. Five Below's consistent positive comparable store sales performance over the last decade shows that its unique concept of selling in-trend merchandise to tweens at cheap prices (mostly $5 or less) is resonating across the country. 

But even after opening stores in new markets, brand awareness tends to remain relatively low for several years around each store, which creates additional opportunities to attract new customers and drive sales growth.

On top of that, Five Below has a very flexible inventory strategy that allows it to shift its merchandise selection to whatever is in demand. For example, the room category saw increases in demand for décor and other accessories during the pandemic, as people adapted to working from home. 

The stock recently surged to a new high ahead of the company's fiscal Q2 earnings report coming up on Sept. 1. Given the opportunities for further expansion, I wouldn't be surprised to see this retail stock double again in the next five years.

The next frontier in streaming

Jennifer Saibil (CuriosityStream): Streaming was one of the biggest stories of the pandemic. But it wasn't only Disney and Netflix that stole the show. 

CuriosityStream produces educational content focused on science and history, and it has partnerships with other streaming companies such as Amazon and Roku, as well as with corporations and educational institutions. It's much smaller than the big guns, with 20 million paid subscribers as of the end of the second quarter, but it has no shortage of content, with 3,000 available titles. Subscriber count increased 56% year over year, and according to ANTENNA data, CuriosityStream had the highest retention rate of any streaming company. That's an interesting tidbit that points to its stability despite its size. It's fairly inexpensive as far as streaming subscriptions go, as low as $19.99 for an annual membership. 

Second-quarter revenue of $15 million increased 27% year over year, and subscriptions increased 40%. Because it's so small, it has a lot of potential to grow. For the full fiscal year, it's expecting an 80% increase in revenue.

What makes CuriosityStream compelling is its niche content. It's not offering another version of the same library of films the bigger companies are providing; it's carved out a niche, and it's attracting customers.

As the company expands, it's still posting losses, and investors have pushed the stock down 15% year to date. But it's not particularly expensive, trading at a price-to-sales ratio of nine. It is somewhat risky anyway, since it's small and unprofitable. But that's also what makes it an opportunity. CuriosityStream appears to have a bright future, and as it picks up customers and establishes more deals, investors could see major gains. 

An asset-lite, profitable business that can expand efficiently

Parkev Tatevosian (Chegg): Chegg is a leading online educational assistance provider to high school and college students. The company offers valuable resources students can use to help get through the curriculum. As of its fiscal second quarter, it has 4.9 million services subscribers. The coronavirus pandemic sent millions of students home, which led to a surge in signups at Chegg. Indeed, revenue growth accelerated from 28% in 2019 to 56.8% in 2020.

As part of a subscription to Chegg, students get to ask 20 questions per month answered by Chegg's experts. These questions and answers are then made available to the rest of Chegg subscribers. Therein lies one of the attractive features of Chegg's business: The company pays for this content once, and it gets used several times. In fact, the nature of the content means it stays relevant for years. 

The surge in usage during the pandemic allowed Chegg to boost the total pieces of content to 66 million. That can serve to add value to current and future subscribers. Moreover, it helps attracts new customers. When a student types a query into a search engine, if Chegg has relevant content, the site will pop up, attracting new users at little cost.

That's partly why Chegg has grown earnings before interest taxes, depreciation, and amortization (EBITDA) by a compound annual rate of 78% from 2016 to 2020. The company spends money efficiently because its content is created specifically in response to what customers are looking for. New subscribers benefit Chegg with additional revenue and by helping Chegg create the most relevant content.

The stock has already doubled since the start of 2020, and it has the potential to double again. It is only in the beginning stages of international expansion, and it is developing its skill-building business.