blue crystal

Render engine is cycles you need to get the plastic roughness only.Also the roughness is in the second tab, you can also change color and add a color ramp if you wish.I just added transmission and a light for better preview and I suggest no HDRI's are needed. Some other details can be added like the voronoi and noise texture, you can apply PBR if you wish and also can be added to a game just don't put the transmission.