Poser 5 with firefly renderer needs other lights (less) than other rendering. The 3 lights setup (main, fill, back is often a good starting point except when you want something special. There are many free light sets available, also here at R. Try them out and try to grasp why and how a result is obtained. Then try to tweak to see how you can come closer to your ideal. Then use Save as to create your own set. Also don't forget to use the Point at option. And start with white lights.

I have tried prudent planning long enough. From now I'll be mad. (Rumi)