For me, the best time to buy bitcoin when the price is too low then that is the best time to invest so you will get surely a high profits and benefits from what you do. If the price is very high and you will saw that it has a big potencial to grow more then hold it a long time i swear you will become a successful person and you deserve it.
If you will be real then you knew already that there is no chance for you to know whether the price will dump farther or it is the lowest point of the dump. The only thing that we can do is to take the risk and decide based on our analysis and instinct if it is the best time to enter in bitcoin, that is why, people like investor not only traders should learn technical analysis.