How to start a linux gui program from the command line without starting a desktop enviroment?

The mentioned programs usually need an X server running. You can run only the X server (usually just by running X). Working with base X is not comfortable, though - that is why desktop environments exist. Why do you need it?

try this:

xinit -- /usr/bin/vlc

this will start a bare X that contains nothing but VLC. not sure if double clicking vlc will let it go full screen, I'm not on my desktop right now. and do note, you need to secify full path of application to run.

I used to use this technique when loading intensive games through wine, and didn't want any desktop effects or background programs affecting performance.