Spin-orbit torque magnetic random-access memory (SOT-MRAM) is attracting considerable interests for which offers sub-nanosecond writing speed, femtojoule-level energy consumption, and virtually unlimited endurance. However, large-scale industrial implementation is constrained by the lack of proper spin-source materials that simultaneously exhibit a large spin-orbit torque efficiency, low resistivity, and compatibility with the established SOT-MRAM fabrication process. Stimulated by recent progress of the complementary generation of orbital and spin currents, we engineer β-W/X (X = Ti, V, Cr, Ru, Ta) multilayers to resolve these constraints. Harmonic Hall and current switching measurements demonstrate that substantially enhanced spin-orbit torque efficiencies and reduced critical switching current densities can be achieved in W/Ti, W/V, W/Cr, and W/Ta multilayers, as compared with that of the pure β-W. Upon further optimizing the thicknesses of Cr and W layers, we realize a low critical switching current density down to 5 × 10⁵ A/cm², which represents nearly an order of magnitude lower than that of pure β-W. The scaling relation between the spin-orbit torque efficiency and resistivity can be qualitatively captured by a charge-orbital-spin conversion mechanism. These results provide practical guidelines for designing energy-efficient spin-source materials that could accelerate the application of SOT-MRAM technologies.