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.
For me its the other way around, I would like to hold to my bitcoin and saved it or long term. So it is also possible to hold bitcoin and to make more bitcoin out of it because once the price of bitcoin rises, your saved bitcoin will have profit positively.