We experimentally investigated the surface plasmon polaritons' (SPPs) localisation, resonance, and propagation in three plasmonic waveguides: graphene oxide (GO), partially reduced graphene oxide (PRGO), and reduced graphene oxide (RGO) in two configurations; as stand-alone structures and when deposited on gold films. Our experiments measuring the nonlinear absorption/refraction and leakage radiation microscopy (LRM) reveal that the intense Lorenz/Fano resonance of surface plasmon polaritons can occur in the PRGO-based waveguide. We also observe an increasing surface plasmon polaritons generation rate in PRGO-supported Au waveguide, a procedure similar to the spaser (surface plasmon nanolaser) mechanism. This, in turn, leads to increasing the propagation length. Furthermore, our analytical simulation results also suggest the suitability of PRGO as a superior optical material for spaser application. Our density functional calculations confirm that oxidised graphene has a more robust absorption spectrum in infrared wavelengths than pure graphene. Additionally, through van der Waals interaction, PRGO forms a more consistent and uniform bond with gold substrate than pristine graphene, reinforcing the suitability of PRGO as plasmonic waveguides.