It is not a stable currency yet so it will crash again several times. Just look at its history and extrapolate into the future with less frequency. You will have several opportunities in the future to buy low, whatever low is at the time. But always consider it a high risk gamble.
My personal opinion is to never go all in on any single investment, max 5-10% on any one thing/stock/commodity, and maybe max 20-25% in any investment area. Crypto currencies is just one area. For building weatlh over the long term, spread it out across real estate, index funds, commodities, bonds, precious metals, crypto currencies, etc.