1. Camera settings
Turn vignetting off. Vignetting creates dark areas in corners of image and usually it isn't desired effect. If you want you can always add it later easily in Photoshop.
To control overall scene brigtness set different ISO or shutter speed.
Turn GI reflevtive caustics on. This allows indirect light to be reflected from specular objects. It will help to lit up scene a bit. Open VRay object properties of the VRay lights, increase caustics subdivs to 8000.
We will choose irradiance map for first bounce and light cache for secondary bounces.
If you don't care about rendering time and want best quality, choose brute force as first engine and set its subdives to 30. Quality of GI in small details will be better, but brute force can produce more noise and rendertime will rise significantly. In Irradiance settings increase HSph. subdivs to 100.
In post-processing (VRay: Indirect illumination rollout), change GI saturation to 0,8. It will desaturate GI a little and colors will not 'bleed' that much.
Increase GI contrast to 1,1.
In Settings rollout when you will Set Global subdivs multiplier to 2 it means that all subdives in lights and materials will be mulitplied by 2. In materials reflection and refraction subdives are set to 8 by default so the result will be 16. This is fast way to change quality of all materials in scene.
You can of course set all subdives in materials by your hand, decreasing and increasing them directly in materials.
Color mapping is set to exponential. It will help to avoid having 'burned out' areas. (RGB = 255,255,255).
Here are all render settings:
Here is final render using this settings without post-production in Photoshop:
Ok, now open Photoshop, we will ad some bloom. Select this area:
When you press CTRL+J it will create layer from selection. Now just add gausian blurr and select blending mode to screen. Copy this layer few times to enchance effect.
Desaturate scene a little and play with levels to achieve final effect.
You may add slight vignetting using 'FILTER' -> 'DISTORT' -> 'LENS CORRECTION'
Also you can sharpen image if its too blury. 'FILTER'-> 'SHARPEN' -> 'UNSHARP MASK'
Final render after Photoshop: