I'll tell you how a person who was making money on cs: go and starting with 1,500 rubles brought 35,000 (this is quite a lot by my standards)
This game has skins. What is it? Imagine the texture of the weapon in the game. It is free (1 photo), but you can buy its analogue with identical characteristics for a certain amount of money ($ 230 (second photo))
So here's how to make money on them. You make a deposit and buy a skin for the price of your deposit (1,500 rubles in my case), then go to https://csgolounge.com/ and put it up for exchange for a skin, at a price of 5-8% more than yours. After some time, there is a person who is interested in your skin and is ready to overpay, provided that he already has the required skin and is ready to change. Thus, a couple of percent is added to your money with each transaction. Without going into details, it works like this. There are schemes according to which you can get 30-35% of the cost of a skin, but these are subtleties. When you accumulate the required amount of money, exchange skins for the required amount of money and you're done.
I'm not going to mention esports, it's obvious. There are sites where you and your friends or random people can participate in daily small "tournaments" for which you get points, later exchange them for prizes, for example, expensive computer accessories, mice, keyboards. But it also costs a lot of points, of course.
Well, having knowledge of maps, you can bet on eSports, realizing that on this map the terrorist side plays the pistol round much easier, so you need to bet on them.