We study the characteristics of surface plasmons propagating along graphene sheets, focusing on the effect of spatial dispersion and applied magnetostatic bias, and taking into account the influence of the surrounding media, applied electrostatic biasing field, and graphene intrinsic features. The proposed technique relates the graphene tensorial conductivity with the admittances of a rigorous equivalent circuit, allowing to obtain closed-form dispersion relations for the supported modes. Results demonstrate that spatial dispersion can dramatically modify the characteristics of the propagating plasmons, even in the low THz band, increasing losses and reducing mode confinement. On the other hand, the application of magnetostatic biasing field leads to extreme mode compression, as compared to usual plasmons on non magnetically-biased graphene or noble metals. These features could lead to enhanced resolution in sensing applications and extreme device miniaturization.