If you can instantly be an expert in something, what would it be ?

Raisins.

I don't need any more skills ,
I need a new spine so I can enjoy the ones I already have
Now if I could make you an expert at spinal surgery
then we would be talking

Medicine

Artificial intelligence. I'd work for Cyberdyne.

Theoretical physics/cosmology

A singer...

Machining. Cnc lathes and the like. It would be useful where I work and a step towards a gunsmithing career.

[b]Sensible answer[/b]: Psychiatry

[b]Not quite so sensible[/b]: Comedy writing

Something that would ensure that I always had a good job opportunity

I'd like to be a kung fu master

Religion