Some samples generated by the V-Ray newbie I am... V-Ray has a quite steep learning curve, with hundreds of parameters whose impact on the final rendering is difficult to grab. So, many hours experimentation sessions are required, as well as tuts on the web. Currently, I'm not a fan, just have a license and make use of it.
The only decent link that really helped me getting in and understanding : https://www.cggallery.com/tutorials/vray_optimization/