Here is some very good advice by Thorsten Weigel on how to invest in Cryptocurrency.
He recommends simple 5 rules:
Rule 1 Go down the rabbit hole
Rule 2 Use CryptoCurrencies
Rule 3 Become a Hodler
Rule 4 Own your keys
Rule 5 Question everything
I recommend to read his full article on Medium.com:
The CryptoCurrency Owner’s Manual
It's hard to say. We have had only two bubbles in bitcoin. We can't make statistics on current data. But basically, everybody has to make their own analysis. If you think about bitcoin (for example) as a future gold then it is undervalued about 150 times for you. If you think about bitcoin as an average payment method, then it is overvalued about 4 times. If you think about bitcoin as one of the main currencies in the future, then it is super undervalued.