Of course bitcoin investment is the best option for newbies like  you because bitcoin is the best coin  to investment in when it comes to crypto investment, though it requires a lot of time and patient before you could profit from bitcoin investment . Bitcoin investment isn't what you can profit from within a short term, but for me instead of losing my money in short term investment I rather invest in bitcoin and hold on to it till the right time.
However, talking about the range of money in which you can use to invest in bitcoin, actually I think you're in the right position to decide on the amount you can use to invest in bitcoin deeping on what you're earning per month. my only advice for you is to invest with what you can afford, secondly you should try and save up some money should incase you need money to settle your bills or any financial problem, this will enable you leave your bitcoin untouched in your portfolio.