I've got an older Gossen Super Pilot light meter that has two modes:
* Reflective when I point it at the subject (similar to what a camera meter does)
* Incident with I slide over a frosted, whitish dome so that the light coming at the object is measured.

* I don't think that "Ambient" really applies here. When you are near the photographed object and look at the camera, the ambient light is incident light.

* When you are using the camera's reflective meter, the ambient light is illuminating the subject.

* Don't worry about flash in this context.

* FWIW: you can get kind of the effect of an incident meter with your reflective camera meter by putting something like a pringle lid or styrofoam cup over your lens. Position yourself near the photographic subject and aim the camera at where you will be taking the picture from.