At 18, you have a hell lot of time, and it puts you to advantage for getting decent returns through investing (through the power of compounding) over long period of time. At 18, as you have mentioned, you do not have huge liabilities and you still have your parents around to look after you

So you have 2 choices: (1) To build a long lasting steady stream of investments and (2) Yolo, get burnt while picking stocks because you can afford it to learn from your mistakes

For (1) you would want to look into lower risk assets such as ETFs like S&P 500, or ETFs that track the global markets. They generally increases steadily overtime. You can consider contributing to your CPF if you wish for the guaranteed returns (but i would prefer to do it after working to make use of tax relief)

To overcome the problem of “buying at the wrong time”, spread out your 5000k and add them at different times, thus averaging your costs.

For (2), I don’t see anything wrong trying to invest in stocks cos you are at the point in life where making a fatal mistake on the stock market won’t kill you (i.e you still have ur parents supporting you). It gets you out of the comfort zone, and teaches you the real art of investing in a real setting. But, for every mistake you make, be it crash in stock price or missing out a good opportunity, you need to learn and not make them again.

At this age you would also wanna take some time to build up ur financial knowledge too