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If I deposit $100 or $120 worth of bitcoins per month from here, how much will it benefit me?...
It would sure benefit you way more than you even see, because it would have provided you with a means of income that if taken seriously would see you gainfully employed and not needing any white collar jobs or answering to any bosses, after you complete schooling.
Also, knowing that you have an investment to look out for, would give you a sense of responsibility to save and adopt good methods to reinvest and earn profitably.
...Is it right for me to invest more $ in Bitcoin than this? And should I invest the whole money in Bitcoin?
It would be wise at this point to be very calculative while making your investment in Bitcoin, because random purchase would sink you further and render you broke, thereby going back to the investment to withdraw and spend of ain't got patience.
It could also make you lose track of your investment because I don't think you know so much about Bitcoin and the best practices to use to keep it safe from hackers and thieves that may know of your investment.
If planting papaya is a seasonal growth plant, then that should also be a concern because a time might come when there ain't harvest to be sold and thus, no funds to invest.