In the world of cryptocurrencies it is so difficult to know when to buy. Instead of trying to 'time the market', just draw some trendlines or use an automated tool (the one I use is: Auto-Trendline from Patternsmart ). Make your purchase once price breaks above the trendline.
In this case, looking at Ethereum on the daily chart, you could have picked some up for $55, $230, and $300 dollars after price broke the trendlines marked with the arrows. Price is listed next to each arrow.