Assuming I can gather 500$ a week from here and there,how much exactly should I invest.
I'm not that greedy and there is no time constraint.
Since you said that you are not greedy then probably you can invest $250 because it is a big money in our country. And make sure that you still have some money in your pocket for emergency case. Investing is kinda risky too but learning about bitcoins will help you a lot not get scammed by others.