All times are good to enter the cryptocurrency market. - Tim Draper
I agree with him, if you invest in crypto for long term, then it really does not matter at the moment when you invest. The world is yet to be tokenized and therefore today's prices (at least the prices of reputable crypto projects) are very low.
There is no specific time for you to invest, as long as you are ready go for it. The best time to invest is when you already know how cryptomarket works and I think we should start on that level. Anytime is good but make sure that you are knowledgeable enough. When the market is dumped, youd better to invest more and hold it for long term until you have made a good profit, expect that the bull will always come to give more opportunities for you.