After making several major mistakes in the past I realized that buying cheap coins and holding them is best idea.
I missed to buy ether because of all "warnings" how ethereum is bad. I had more or less 100 dash when its price was 4$. I had lots litecoin which I have sold for - 10$. I had lots altcoins in january 2016. and I've sold them all. I sold my bitcoins for 500$. Last year I sold them for 2400$.
I regret all my past decisions.
Don't worry. You can still make an investment plan and buy into some promising coins and hold on to them. Crypto is still growing and my philosophy is sell them only if you badly need money to achieve your financial goals. Otherwise it's a HODL for me.