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.
If $30 is what he can afford to start investing in Bitcoin, why not? Isn't it good that he just want to try first in small value to experience investing in Bitcoin? It might really different for some investors who started with huge capital but it's not an issue here. What matter is he started his journey regardless of the capital he use to buy, it's the start for him to grasp how it really works. Then he can decide later on if he wants to continue buying more, the market is unstable and there's always a chance to buy Bitcoin if there's a correction.
Just guide him so that he will not be tempted to commit a wrong decision along the way, that's what you can do to help him to be on right path.