I am investing money in the stock market for more than 20 years now. The one thing I have learned when looking back, is that an investment was successful when I knew about the subject.
Rule No. 1
Only invest when you know about your subject.
I don't own a car, nor do I know how to repair one or how it works exactly. So I don't invest in automotive. But I know about Computer Games. I develop one at the moment and play every day.
Check out my Wikifolio: https://www.wikifolio.com/de/de/w/wf000g4mes