your cheapest option is PLA. I would recommend PLA + or aka PLA Pro. It has a bit more heat handling ability. Leaving PLA prints in your car on a warm sunny day can be rather bad for there health. And just because your printer doesnt have an enclosure doesnt mean you cant print abs. It helps. Abs is very prone to warping in the print stage. So a heated bed is essential. An enclosure just help a bit more and a basic one can be build out of sheets of plexiglass. In an old house like mine prone to wide swings in house temp and air currents ABS printing is rough without said enclosure..I have recently purchased a 3D printer and want to print Halo 3 MKVI armor. What is the best type of filament to print armor with? I probably can’t print ABS the compatible Filament list says I can but the printer isn’t enclosed.