If you're good with computer graphics and programming, you're halfway done for doing your first demos / experiments :)

If you have an OculusRift, I think that's probably the easier start. Not because "mobile" is harder, but because you can focus more on doing stuff instead of optimizing / cutting stuff because mobile devies still do not have so much computational power.

Unity3D / Unreal engine are really easy to set up for VR. So easy to set-up that most people lose sight of VR.

I HIGHLY suggest you to give a read here https://developer.oculus.com/documentation/intro-vr/latest/c...

and

http://static.oculusvr.com/sdk-downloads/documents/OculusBes...

You may think this is simple, everyone do it but... no. There are so many useful hints about how to reduce sickness and produce a better product, and so easy to find, that is mandatory to know.

This will get you started pretty well :)