One good way to also invest in Bitcoin is that the person must have a target price at which they want to buy, so that if the price drops to or below their target price, they will just buy at once. In the case of my example, the price of Bitcoin fell way beyond the investor's target, and even if they bought up at once, it's never a bad investment, because their profit will still be huge compared to others who might have even bought at $30k or those that bought Bitcoin during the last bull market at $40k, $50k, and some at $60k.
Buying in the 40k-60k range is not a good target, it tells us that the investor has done some poor analysis before investing. And in this case, buying in one trade is bad, because in the further fall, if he continued to buy in parts, he could get a better entry price. But I'm not opposed to buying most of the investment in one trade, it can also get a good price, although this requires good market reading and to some extent it will still be a game of luck.