Naturally, the speculative approach requires an understanding of the properties of the market, the nature of the various trading instruments, long observation of the charts, the existence of a serious, reasonable trading system.
Buy fast, sell fast, it is a short-term strategy characteristic of non-investor traders. Because the trader has the principle of a little profit is enough, then buy again then sell again even though a little profit. The constraints must be large capital and the implementation time must be fast, because the price is not stable. This type of transaction is more dynamic than investment, HODL long waits until prices rise.
Cryptocurrency trading is according to the market situation. You cannot buy and sell fast. First you should see the price of bitcoin. If you think that it is right time to buy some coins and it will give me some profit in the future, then you should buy, but keep in mind that demand in these days is low and selling is not as easy as you think. You will not find buyers easily in the market.