Some key points of financial advice that all teenagers should learn:
0. Always invest at least 10% of what you earn (more if possible), and never take on debt other than a mortgage. If that means sharing an apartment with roomates instead of having your own, having an old phone from eBay instead of a shiny new iThingie, driving an old Toyota instead of a new Audi, etc. do it.
1. Risk is a function of time. Equities have a reputation for being volatile and risky, and they are, in the short term. In the long term, it's the opposite - there is no investment that consistently earns more. When you are young, you can safely be 100% invested in equity funds that are index based (thus diversified, like mutual funds or ETFs based on S&P500, Russell 2000 or other broad indexes).
2. Savings accounts, CD and other "safe" cash instruments usually earn less than inflation. Their risk-time profile is the opposite of equities. Short term they are the safest. But long term they are the worst as they guarantee that you will lose all your money (however slowly). They may be a useful tool for occasional use, but they are not a primary investment.
3. Timing or gaming the market is impossible in the long term, no matter how smart, well informed or professional anyone is. So avoid actively managed funds or any other strategy that relies on knowing more than the market. They have higher fees and never beat the market in the long term.
4. As your long-term investment end goal approaches, you have less time to recover from potential short-term losses. This means your risk-time profile has changed. Gradually shift out of equities into less volatile instruments to safely lock in your long-term gains. To make this easy, you can invest in indexed funds that make this shift automatically, based on target retirement or end-goal years.