I personally use the stock market.
I started with getting subscription money from fucking until I had a budget of 5000$
Then I went to the cheapest stock and invested all my money other than what I needed for food and rent.
I did that when the price was at 7$ per stock
I then went to bed in 1h intervals while checking the stock market inbetween naps.
everytime the stock price has increased I saved and if it went down more than a dollar I reloaded the last save.
That's how I bought stocks for 7$ and sold them for more than 100$.
Did the same thing in reverse until the price was back at 7$ and invested again.
I then did that over and over again but with a lot more stock and now I have well over 200.000.000$ so I'm good for the forseeable future.