What should you do with extra $100? Here's what financial experts suggest

Seemingly all of the known universe is tilted against Millennials saving money.

Young Americans face lower lifetime earnings, lower investment returns and the slow and shameful death of the pension system.

Two-thirds of Millennials hold long-term debt such as student loans, the Wall Street Journal reported last year, and 29% of those with bank accounts recall overdrawing them.

Deck is stacked against Millennial savers: Here’s how to succeed

So say you’re young and defy the odds: You navigate the economic wasteland left by Baby Boomers and come upon a spare $100. What’s the smartest thing to do with it? Save up, pay down or invest, as Millennial money experts told USA TODAY.

“It's not about $100,” said Sophia Bera, a financial planner in Austin who founded Gen Y Planning.  “It's about what habit you're going to create to get your finances in order. It's about investing $100 every month, not one time.”

But for that first $100, consider these tips:

Build an emergency fund. Like, yesterday.

“First and foremost, you need to build a savings buffer,” said Stefanie O’Connell, a personal finance expert and author of The Broke and Beautiful Life. “Even if you have student loan debt or high interest credit card debt, that first $100 can and should kick start your savings for an emergency fund.”

Building up an emergency fund of cash provides a safety net should an unexpected expense arise, keeping you from taking out high-interest debt. Save at least $1,000 for it at first, O’Connell said, but eventually aim to build it up to six months of living expenses.

“$100 can get you 10% of the way there,” she said.

How to build the perfect emergency fund

Pay down that debt

Already funded for emergencies? Then consider any debt, said Tyler Dolan, a financial planner for the Society of Grownups in Brookline, Mass. It’s one of the biggest reasons Millennials live paycheck to paycheck, he noted.

Both credit cards and student loans can carry high interest rates, Dolan said, so aim at whatever debt has the highest interest rate first. Over time, you can save on interest payments and even decrease your repayment period, he said.

If you owe a $50,000 student loan with a 7% interest rate, putting $100 toward it each month would save you more than $4,000 under a typical 10-year repayment program, Dolan said. That ain’t chump change.

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Invest it somewhere

“You may also be thinking: Where do I even invest my $100?,” Dolan said. If that’s the case, check first with your employer to see if it offers any sponsored retirement plans such as a 401(k), he said.

Any investments in these would technically come out of your paycheck, not your precious $100. But if you have extra money to invest, many employers will even match your contributions to a certain percentage. (Translation: free money.)

If you don’t have a 401(k), Bera suggests setting up a Roth Individual Retirement Account (IRA). Any money put into a Roth IRA has already been taxed, letting your investment grow tax free. Bera recommends setting up a Roth IRA at Betterment, an automated investing service where your $100 can act as your first monthly contribution.

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Follow Josh Hafner on Twitter: @joshhafner