It always depends on what you want to achieve with your money? So you have an income of 600$ per month, i guess you have also a lot of fixed costs, so let's say you have 100$ of spare money left each and every months, then i would still put aside 50$ of that for savings if something unforeseen happens and the other 50$ you can use for your investments. If you want to invest into relatively stable projects then you should choose projects like Bitcoin and Ethereum, usually they suffer the least in a bear market. If you say that you want to go high risk with that 50$ then invest into new and upcoming projects. There you have the possibility for high profits but also for a total loss.