After Effects experience with virtual choir 3D environment
This is a tricky video production technique. Anyway, try the following steps:


First, create 4 black solid layers. Then, add a Lens Flare to them. 

Place one flare in the bottom right corner. 
On another solid, make the lens flare on the fare right middle. 
For the third color solid's lens flare, make it on the top. With different color flares, it will look closer to what you are after. 
Then, add a Ramp behavior to the last black solid and make sure it is on the bottom of the other layers. 

Also, make the top a light gray and the bottom a dark gray. 
Add an Adjustment layer above the black solids. 

Add a Fast Blur to it and set it to around say 60, making the lens flares blurry.

Select all of the layers and create a pre-comp. 
Meanwhile, try to add another color solid and make it white. Then, add a mask to it and make it an oval shape. Make the feather big like 250 or more. Move it so it is where the floor would be.