The goal of this paper is to offer criteria for the material determination of core-shell structural particles in order to enhance the electrorheological effects obtainable with suitable combinations. Based on electrical and magnetic theories, the core-shell structure is investigated using the point-dipole approximation method to produce an electrical potential solution that satisfies the Laplace equation. A better structural combination is determined based on the mathematical results. The results show that the conductivity ratio dominates the ER response when the external field frequency is low. Conversely, the ER response is dominated by the dielectric ratio when the exterrial field frequency is high. We choose a material with higher conductivity for the solid particle core or for a structured particle core-shell skin as long as the conductivity ratio or the dielectric ratio of the solid particle to the oil medium is greater than one. The best material choice is a metal when the overall conductivity of the fluid is not very high. This study used a simple model that explained all of the experimental results, which are presented here as a reference for dispersed particle fabrication in an electrorheological fluid.