I'm preparing for the college entrance exam to go to college, so I can't make money from working. I get about $100 of allowance from my father every month. I use all of them to buy bitcoin because I can use father's credit card for expenses such as food, clothes. I can buy Bitcoin on a satoshi basis every month, but when I see people buying Bitcoin basis on the internet, I feel like I'm too behind myself. Maybe they have a much higher income than me because they have a job. I think I can only invest $100 a month for the next year or two, would that be enough? I am worried about missing big bull market with halving and etf approval.
Investing 100 USD per month in Bitcoins as a student is totally fine and you shouldn't be giving yourself a hard time about it. Since you don't have any income yourself and fully rely on your parents to take care of you, it's already a lot to set aside 100 USD for investing. I assume that is the money you could be spending going out with friends during the weekend or go watch a movie, have a nice dinner, etc. So, cutting back on your personal expenses to start building a crypto portfolio is fine and should lead to some decent long term profit. Don't worry so much about missing out on the next bull run, because there will also be the next bear market around the corner which will send prices down again. Crypto markets always tend to move in cycles and you will find another good time to invest in. Focus on your studies and then you can buy much more cryptos once you graduate and have a well-paying job. Another thing could be to find a student job that gives you additional income without impacting your studies. That additional capital you could be using to buy more Bitcoins per month.
Even though he relies on his parents, it's smart to save $100 a month. A good mix between enjoying the present and making money in the future. It's mature to put investments ahead of meals and trips. Diversifying your investments is important, though. Back Bitcoin, but don't forget about other crypto and non-crypto choices as well.
But caution is very important. The crypto market is unstable, so you can make money or lose money. Long-term wins should be more important than market swings. Your plan should last a long time and stay the same even if markets change.
When invest, think about jobs and schooling. As you said, getting a part-time job could help him make more investments. Never at the cost of your schoolwork. In terms of job and money, education is an investment that pays off.