investing money in PTC website, buy a golden or premium membership and rent about 200 or 250 members according to your budget (300$), and you'll get about 77$ per month
If you want to get an income of $60-100 per month with $300...then you can use $300 your money to buy some domains and then you can plug in your domains with chitika ads or google adsense or infolinks ads and much more others ... Good luck ...!!! Remember...!!! Don't fear failure because failure is the beginning of a success.