Hard to tell exactly what you want to do. You might as well finish it. If your walls are straight you can put furring strips up with drywall and a drop ceiling. Probably the cheapest and an easier way to go.

Our unfinished walls were insulated and covered with poly. Which is something we would do anyway when finishing the basement. Maybe you could do the same for the ceiling?

What is poly?

Poly is short for Polyethylene. Basically, plastic sheeting. Its sometimes used as a vapor barrier for interior walls. See link for an example...

Here is a link that might be useful: Polyethylene Sheeting