One thing that you must know to buy altcoin for hold long-term, don't put your money to buy at the same rate. I mean after we have decided what coins that good to invest in, let's buy it gradually until we have the cheapest price. Also, you must have good money management to do it.
The major problem is Crypto is so unpredictable that no one knows the bottom so trying to buy cheap might not be cheap afterall. The most important is no 3 o his list buy solid coins in which even if the price reduce its just a matter of when if the investor is patient enough