There is no single right answer as to what the ambient value should be set at; for a large area mesh, 1 may be just right, whereas for a small intense light such as an LED indicator light, you may need it set to 70.

Simply jacking up the ambient usually results in the light itself appearing very bright, but only weakly casting light.

In Firefly, I use an "IDL emitter" mesh outside of -but closely fitted to- the light mesh. With the emitter property set to not cast shadows and not be visible in camera, I crank its ambient way up, while the visible light mesh has a moderate ambient value. The result is that the light's apparent brightness is matched by the emitter's lightcasting strength.

In Superfly, you don't need a hidden emitter mesh; you can use a LightPath node and do some color math to get the camera to see more light cast from the prop.

Some glowy demo freebies

. Other freebies (many have meshlight parts)

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5