Just like stock, you can invest all your money for a coin code if you really trust. But that would be very dangerous. One can make sure that the coin will not fall down to 0 a day.
The advice is to diversify your portfolio. That will help reduce the risk. You do not earn much but if not lost also much.
yes.some invest in bitcoin and some invest on litecoin,eth,ripple if one thing goes up obvisouly one thing goes down so its better to invest in multiple coins