If you absolutely cannot pay for V-Ray, consider switching render engines that have built-in libraries:
Since V-Ray works best with *.vismat files, use a free script: Sketchup Vray Material Library Free Download
: Offers a generous selection of professional-grade free materials for architectural renders. If you absolutely cannot pay for V-Ray, consider
: Thousands of high-quality, scanned, and CG photorealistic materials. Sketchup Vray Material Library Free Download
You don't need a "V-Ray specific" library. You just need high-quality textures and a free material converter.