The stock market remains one of the best ways to grow capital over time. And although having millions in the bank might help, a more accessible -- and perfectly sensible -- strategy is to invest relatively small sums regularly. Even $200 can go a long way, provided it's invested in quality corporations that can deliver excellent returns over the long run.

There are many such companies on the market. Let's consider two examples worth investing in now: DexCom (NASDAQ: DXCM) and Novartis (NYSE: NVS) .

1. DexCom

DexCom is going through a rough patch. Following its second-quarter earnings report, the company's shares dropped off a cliff . But even including this decline, DexCom's shares have outperformed the market over the past decade:

Note that it hasn't been a smooth ride -- the diabetes-focused medical device specialist has experienced several corrections similar to its most recent one over the past 10 years. But unless DexCom's long-term outlook has changed, it's still worth investing in the stock, especially while it remains down.

Management pointed to several reasons behind DexCom's mixed second-quarter results and disappointing third-quarter guidance. First, the pace of new starts for continuous glucose monitoring (CGM) devices isn't as fast as hoped.

Second, revenue per customer in the U.S. is declining because patients took more advantage of rebates for DexCom's newest CGM, the G7, than the company expected. The issue with rebates is a short-term one.

The more important problem for DexCom is whether it can remain competitive against its biggest rival in this field, Abbott Laboratories . Fortunately, these two leaders have only begun to scratch the worldwide CGM opportunity. As Abbott reported earlier this year, there are half a billion (and the number is growing) adults in the world with diabetes, only 1% of whom now have access to CGM technology.

There are challenges for DexCom in accessing most of these patients. It doesn't operate in many countries with a significant number of diabetics. Most patients reside in developing countries, where most might not be able to afford CGM devices.

Still, DexCom has made headway and entered new territories over time. Last year, it made its entrance into South America by launching its DexCom One in Argentina. The DexCom One is, among other things, a cheaper option for price-sensitive customers and regions. The company should continue developing newer, better, and hopefully more affordable options that will allow it greater access to patients worldwide.

DexCom's revenue and earnings have grown significantly over the years. I'd wager that DexCom still has years of market-beating potential. And with $200, you can afford two shares with change to spare.

2. Novartis

Novartis is one of the most prominent pharmaceutical companies in the world, and boasts a large lineup of medicines across multiple therapeutic areas. Unlike the more volatile DexCom, Novartis is a picture of stability, making it an excellent pick for low-risk investors. True, the stock has underperformed the market in the past decade:

However, Novartis recently started a new era after it spun off its generic-drug unit into a stand-alone company. The generic-drug market is a ruthlessly competitive one where it's hard to build a competitive advantage since, unlike novel therapies, generic medicines don't benefit from patent protection.

Novartis will focus exclusively on developing brand-new drugs from now on. Some of its newer approvals include Fabhalta, a therapy for paroxysmal nocturnal hemoglobinuria (a rare blood disorder) that earned the green light in the U.S. in December. And the company is currently awaiting approval for atrasentan, a potential therapy for a kidney disease called IgA nephropathy.

Novartis' top-line growth rate should improve in the medium term thanks to newer approvals, and to the fact that it no longer has to deal with its former generic-drug unit. In the second quarter, revenue increased by a solid 9% year over year to $12.5 billion. Adjusted earnings per share were up 17% year over year to $1.97.

Novartis is also an excellent dividend stock, having raised its payouts for 27 consecutive years, an impressive streak that speaks volumes about its business. Shares are changing hands for just under $112. With $200, you can get one share, with enough change to spare for another quality stock.