Honestly, that’s up to you because we don’t know which price will go up. If you think, you can take the risk, then you can buy. Or else, if the price goes down, you can buy at the dip. So, analyse the market and take risk accordingly.
We usually call cryptocurrency is the most volatile because its color can change quickly at any time. The price you are waiting for may not come again or may go deeper than you expect. But normally if BTC in between $20k to $25k then it is enough to buy any asset. A small price change may not have a big effect. Since the market is now at $21K. So it implies the best time to buy any assets.