There's no such thing as a good rate to Invest in Bitcoin, because the Crypto space is Volatile.. I.e expect anything to happen anytime. You might buy at the rate of let's say $12k and the next day it dips further to $10k, u would have felt, you should have waited right?? Yes!. But one thing you can always be sure of is that the King Bitcoin would always rise beyond Its pairs. So when it dips BTFD. It would pay off if not in the Short run but surely in the Long run