It seems to me that bitcoin is the best currency to earn on the course. The price is not very stable and fluctuates constantly in different directions. It is possible to earn and gain experience for the transition to earnings in other currencies.
Yes, you can learn how to earn money on bitcoin. But it is suitable for short-term investments, because it is very unstable and no one can tell exactly what will happen to it in a few years.
In order to make money out of money bitcoin is better than any other currency. The principle of earning on the money is a short-term deal. For long-term investment it is better to use stocks and gold. I certainly admit that bitcoin price will grow further, but it's a big risk. Those who are willing to risk can become a millionaire, and may lose all their savings.