I think you could purchase when the price down to your price target. If you are hesitant, the price of Bitcoin might be would fly next moment.
If you serious in bitcoin investment then no need to wait more, you should invest today because those who only think will think ever and will never step forward. I think this is the right time for bitcoin investment because the price is low and dont be greedy to wait for more dip, may be the price grow more and you miss this chance to buy bitcoin for low price.