I prefer to buy at once and wait a big increasement in price to sell. I'm following the chart hoping to catch the right moment when the price will start increasing again without falls like now.
You say that buying in smaller increments is risky, but if you go all in at once, you risk seeing the price move in the opposite direction, and thus you're not able to open or close positions after that.
In my example, if the price goes up, you'll have some coins in your pocket to cash out. If the price goes down, you'll have some fiat that you can use to start buying at lower prices.
You're aiming more at luck than something that involves thought and a decent level of market analysis. I personally find your approach far too risky, but after all, it's your choice.