In this study, material development, characterization, and sustainability assessment are performed on blends from recycled post-consumer commodity plastics for fused deposition modeling (FDM) filament extrusion. A recycled polyethylene terephthalate (rPET) and high-density polyethylene (rHDPE) blend 80:20 ratio is modified using three different methods: compatibilization with Maleic Anhydride, surface functionalization of PET with sodium dodecyl sulphate (SDS), and hybridization by combination of the two methods which is a novel approach. The selected blends were reinforced with chopped glass fibers and characterized. The printability of blends was assessed, and the dimensional accuracy of the prints was calculated. In addition, a cost estimation and comparison between the developed blends and the commercially available FDM filaments was carried out. Finally, life cycle assessment (LCA) was conducted for each prepared blend to facilitate the decision of the optimum blend in relation to mechanical properties and environmental performance and hence correlate the material, economic, and sustainability advantages.