The point is not to make bad financial decisions, if only obsessed with collecting a lot of bitcin but we have a little money do not put it into Bitcoin all because it will interfere with long -term investment/collection of bitcoin, until you sell your bitcoin because you don't have money to buy needs You are everyday.
We have to ascertain whether he has any other income apart from receiving $100 every month from his father, he lives separately from his parents and if he has no other income then $100 every month is not enough for any investment, the impact of inflation is living in another country then we have to saves to meet daily needs, but if he could allocate $20-30 it would be better invested in bitcoin.
I like OP's motivation for wanting to invest in bitcoin, but I hope he has other income to invest more bitcoin before the next bull run, I suggest he learn about earning from crypto events and signature campaigns to increase income to buy more bitcoin for investment long-term.
Yes it would be better if you have other sources of income besides giving his father to take the best steps in investing in Bitcoin, I agree with you $ 100 is not enough for any investment, unless he wants to invest every month and set aside money from his father to invest in Bitcoin any amount He invested, so I suggest him to see the budget of his needs first before making an investment so that his life is also in good financial regulations.
His initiative is good, I also really appreciate it, if you speak the signature campaign, I think it will be difficult for the OP, he must have a lot of contributions in the forum to raise the rank to enter the classification of the requirements that are usually done by the campaign Manager, but if he is people The persistent who will definitely get the job and get additional income from the campaign signature.