Someone ask me a question after introducing bitcoin to him, if he can start up with $30 and grow with it but I told him bitcoin is wide and high in volume, price and market, that's means whatever you're starting with determine the outcome of the market like for example; if you start with $30 and eventually the market goes up to a little increase of $32 can not be compared with someone who started same time with you, at the rate $100.
That's not the way to encourage people to invest, he can even start at $5 and check the progress of his investment, when he sees that it's growing or increasing he will add more, don't ask people to be greedy right away, its always been invest at the amount you can afford to lose
So also when the market is down to some extent, the person with $30 may likely loss more because of the money is small. Blockchain has the minimum amount one can invest if am not mistaken but if your amount is too small may be difficult to make easy progress.
If he is properly educated on investing he'll accept that fact, but let him invest at whatever amount he likes and what he thinks is comfortable enough, educate him more, and let him decide for himself if he wants to add more.
What do you think about my advice to him?
In my opinion, it's not good there was a time I gave a friend $5 as a starting point after a year he already invested over $5k and he is still good, so to encourage others to invest he gave them $5 as starting investment to see how it works and to learn how bitcoin works.