Investing is best when it's focused on the long term, as this allows compounding to work its magic uninterrupted. Buying and selling individual stocks can be lucrative, but success is not a sure thing, and it's rare to find businesses that investors can own indefinitely.

That's why I believe one of the best things you can do is consider owning an exchange-traded fund (ETF). And there's one leading asset manager that offers some of the best products out there. Here's one Vanguard ETF to buy with $100 right now and hold forever.

Betting on the American economy

Investors are probably familiar with the S&P 500 index. This is the most closely watched indicator of the stock market's performance. It contains the largest 500 businesses in the U.S., and by owning this collection of stocks, investors get to bet on American entrepreneurship, growth, and innovation.

One of the most popular ways to invest in these stocks is by buying the Vanguard S&P 500 ETF (VOO -1.21%). It's offered by one of the most reputable asset managers out there, Vanguard, which has a history that spans five decades. Investors will have peace of mind knowing that $1.4 trillion in assets are in this ETF, showing the trust investors place in it.

This index is weighted by market capitalization. So companies like Apple, Microsoft, and Nvidia, which are the most valuable in the world, have a huge influence on the ETF's performance. On the other end of the spectrum, there are plenty of lesser-known names as well.

Solid performance at a low cost

Performance is certainly one of the top factors that investors pay attention to with any investment. In the past decade, the Vanguard S&P 500 ETF has generated a total return of 233% (as of Feb. 28). On an annualized basis, this translates to 12.8%, which is a wonderful outcome.

Another factor to focus on is cost. If you pay too much, fees can eat away at your returns. Luckily, the Vanguard S&P 500 ETF sports a minuscule 0.03% expense ratio. On a $100 investment, this equates to just $0.03. You keep more of your money over time.

Besides solid performance and a low fee, an underrated benefit of buying and holding this ETF is that it requires zero commitment of time or effort. There's no need to spend hours poring over financial statements, studying management teams, or running spreadsheets. 

Play the long game

As of this writing, the S&P 500 is off about 5% from its peak, which it hit in February. Any slight dip in the broad index can be viewed as a good buying opportunity.

But even if the index were at a record high, it's still a good time to put money to work. That's because over the very long term, patient investors are generally rewarded. While the market is unpredictable in the short run, over any 10- or 20-year period, the S&P 500 is likely to produce a positive return. Remember this anytime you're thinking about waiting for a pullback before investing.

It's a smart idea to buy $100 worth of the Vanguard S&P 500 ETF today. But an even more lucrative move would be to dollar-cost average. This means allocating more money, say $10 or $20, extra per month or quarter to your portfolio. This not only helps to build a habit of investing, it ensures you are able to take advantage of multiple price points.