Advancing epoxy composite technology requires innovative matrices and functional fillers. This study introduces a system formulated from a tetra functional epoxy resin (DABA-EE), synthesized exclusively from 2,2’-diallyl bisphenol-A (DABA) via a dual epoxidation approach targeting both phenolic and allyl groups, as confirmed by NMR and FTIR analyses. The resin was cross-linked with 1-(3-aminopropyl)imidazole (API), and a series of composites was prepared by reinforcing the matrix with sustainable, high-performance materials. These reinforcements/fillers were functionalized bio-silica from Bermuda grass (FBS), activated bio-carbon from Palmyra sprouts (FAC), and graphene (G). A comparative analysis of the resultant polymer composite materials (DABA-EE-API-FBS/FAC/G 5–25) versus the pristine epoxy polymer (DABA-EE-API) demonstrated substantial improvements. We investigated the effect of these fillers on thermal and dielectric properties of the composites. All of the composites had surfaces that repelled water, with contact angles against water greater than 100°. The graphene-based composite DABA-EE-API-G25 exhibits an extremely high dielectric constant of 100.02 at 1 MHz, due to a greater number of charges being built up at the graphene-epoxy interfaces.