... This can be a decent and reliable strategy. Buying at lump sum creates a risk on your capital, so buying gradually is a better trading strategy.
What you are writing about is called DCA (Dollar-Cost Averaging), and this strategy is completely unsuitable for trading, as it is the best tool for an investor. And this is due to the fact that trading requires a trader to react immediately to market changes, while an investor using DCA buys coins regardless of its value in equal installments after an equal period of time.