Hello. So I'm making this game that is set on a planet. The whole planet is rendered with about half a million faces. I'm using a directional light; however, there is a specific rim of lighting effect that looks optimal and shows off the contuors of the planet nicely. If I use an ambient light then the effects of face normals are disregarded. Does anyone have proposed ideas on how to light a whole sphere uniformly. Showing off contours and what not?

The standard thing to do for ambient lighting these days is pre-integrated IBL (aka pre-filtered environment maps), as popularized by Brian Karis in 2013:

https://placeholderart.wordpress.com/2015/07/28/implementation-notes-runtime-environment-map-filtering-for-image-based-lighting/
http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_slides.pdf
http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf

Oh boy, o.k I'll try to figure those links out. Thanks.

If I use an ambient light then the effects of face normals are disregarded. Does anyone have proposed ideas on how to light a whole sphere uniformly.

Not sure what you are trying to do. Full ambient lighting will assume every face receives all the ambient light, so if your ambient term is 100% then face normals won't matter.