Seems like a stake in a business and real estate are two ways that people have reliably made money.
A high paying profession is another way, but that involves and one for one trade. You have chances to make more money by doing things that scale.
However, to start, you need to have money. So you can make your first amounts of money with sales. And a normal job. And being frugal and saving.
Investments. Well, they are possible, but you need a skill / edge. You need to be in the right place at the right time. Usually helps to know the business, the sector, management, and broad market movements. Investing in the stock market is interesting because it is like you can play at a lot of different games.
Once again, though, you have to ask... to what end?
Obsession with being 'successful' aka rich is like obsession with beauty.
Success is not only having money.
"Having Money Isn't Everything, Not Having It Is"
– Kanye West