"so render time is a huge consideraton too."

If you're doing an animation, Ambient Occlusion (at values that look good enough) will seriously increase your render times. Don't bother with it yet, nor any other of the "advanced" stuff. Get your anim working first, then think about improving it where necessary.

Animation doesn't (usually) need anywhere near as much "realism" in rendering terms as is needed for stills. The eye gets caught up in the motion and fills in the details for itself.

Hope that helps,

Cheers
Diolma