In this study, three types of silver nanostructures, including multi-shaped silver nanoparticles (MAgNPs), silver nanospheres (AgNSs), and triangular silver nanoparticles (TAgNPs), are developed, and their functions for surface-enhanced Raman scattering (SERS) application are investigated using both experimental and theoretical approaches. Particularly, the effects of Ag morphologies, excitation wavelength, and inter-particle gap on their SERS performance are focused. Simulation results show that MAgNPs possess a local-electric-field enhancement factor more than AgNSs (ca. 124 folds) and an electric field wider than TAgNPs. Materials characterization results show that the optimal excitation wavelengths of MAgNPs and AgNSs are in the range of 560–590 nm. Thus, employing the Raman laser source (532 nm) is highly suitable for exciting the SERS effects of Ag nanostructures in this study. For demonstrations, the MAgNPs-based SERS substrates are prepared by coating MAgNPs suspension on Si substrates. These substrates demonstrate high sensitivity to Rhodamine B (LOD of 10−13 M) with consistent reproducibility, robust durability, commendable selectivity, and impressive reusability. The results indicate that the experimental outcomes align with the theoretical simulations. These attributes collectively make the MAgNPs-based substrate a promising candidate for practical applications in Raman techniques.