“If you don't find a way to make money while you sleep, you will work until you die.”
Warren Buffett
When it comes to anything in life, the most potent ingredient is time. It's true for barbeque, healing, learning, and for your money. Invest your money. Invest it early and do it consistently. If you start investing in your early twenties, you will beat the Wall Street speculator with your decades of consistent investing, every time.
Pick a simple mutual fund. Find one with low rates (a lot of people recommend going with Vanguard and I agree with them) and find one that's diversified. I recommend anything tied to the S&P 500 or the equivalent for your country. The S&P 500 is the top 500 performing companies in the US market, so you're guaranteed growth over the long term.
You're not Warren Buffett. You're busy becoming a linchpin. Plus, there are a lot of smart, motivated people working tirelessly to ensure the success of the US stock market. Let them do the hard work and you reap the benefits.
Live below your means. Enjoy your lifestyle. Invest what's left. Do that from the start of your career, and you'll be surprised what it turns into after a couple decades.