You never know when the price stops falling.
You can buy the coins you want with your available money at once, or (as I do) divide your money in 3 - 4 parts and start buying using every time one part of them. I think it is called dollar-cost averaging.
This strategy is a way to avoid the volatility of the market because you are averaging prices over time.
You took a good desision buying at the dips, you'll never make money just sitting on the sidelines