Congrats, you’re off to a great start. I would invest in passive index funds but you have to understand why. The most important investment is in your financial education at this point. If you listen to Choose FI and the Money Guy Podcast and read JL Collins The Simple Path to Wealth you will learn how to set yourself up for financial success.
I might also read Why The Stock Market Goes Up by Brian Feroldi. The fact that you even paying attention to your finances so young puts you on the right track.
What is your income? What percentage are you saving so far? Your expenses are very low? Are you living at home?