The bigger the better should be the motto here since it will allow you to see better, but generally, anything around 3 inches to 4 inches will be good. Don't go under 3 inches or you will have trouble following the instructions written on it.  3D printers under $500 might seem impossible to get especially when it comes to getting good working models. But it is indeed possible. These printers come with great build sizes, software, technologies, and more. You can use these to make your projects or use them in an educational space to teach children. Overall, these are versatile in their uses.