When advising someone concerning a good digital currency for investment it's best to advice the person to focus on the one that's more decentralized, Bitcoin is the best amongst all that suits that description, no other ones come close to it, even though some people do feel their are good alternatives for investment but none have been more secured like Bitcoin.
Anyways Bitcoin investment is not for everyone it's for those who have hope in it and believe that If they can remain calm and patient while accumulating it continuesly they'll get better reward in the future, although some people still choose to risk on other coins asides Bitcoin but the best coin for investment is Bitcoin and no other.
You should never advise anyone to invest. Because if you tell your friend to invest in Bitcoin and if he invests in Bitcoin and after a few days the price of Bitcoin decreases, then he will get very scared and then that person may sell his holding. Then he will put the entire blame for this loss on you. Because you gave him advice.
This is exactly what happened to one of my friends: A friend of mine invested in Bitcoin. He told a friend in his office about his investment, will you do it? He asked his friend to invest directly without saying anything about the risk etc. A few days after investing, suddenly there was a fall in the market and when the new person saw that his investment was losing money, he sold his entire investment. The entire amount of money he had lost was completely blamed on my friend and he had to pay full compensation. So you should never advise anyone to invest. If a person comes to you to learn something about investing, you can tell him the basic knowledge about Bitcoin and show him some videos and say, "This will be useful for you."
It is only when you tell your friend the sweet part of Bitcoin investment you will take all the blame if your friend lose his money in Bitcoin investment because you made your friend believe Bitcoin is a quick to get rich scheme, and it can make your friend to use the money meant for his/her expenses to invest in Bitcoin. If you must tell your friend about Bitcoin, make sure you tell your friend the good and the bad parts of Bitcoin investment so that he/she will be fully aware that Bitcoin investment is a long term investment and he/she needs to use his/her discretionary income to invest in Bitcoin, and it will help to eliminate any blame that may arise in the future.