I started investing nearly 20 years ago in my teens. I've learnt a bit in that time, but would say I'm still learning a lot every year.
I think a good place to start is self-awareness; understanding your own personality, risk tolerance, financial priorities, etc.
Like Niloony said, very worthwhile to read as much as you can to improve your knowledge. Reading about economic history, financial market history, successful investors etc can be very helpful.
I also agree learning how to read financials in reports is crucial, as well as information on different investment theories and techniques.
Only take advice from those you know and trust, but better still, develop your knowledge and understanding to be able to trust your own judgement.
And never underestimate the power of compound growth. Starting early rather than later is a big plus. Same with altruism - start early in a small, affordable way, and it will become a habit that can grow with time.
