How to Insulate a Garage Ceiling
When using fiberglass insulation, the conditioned space needs be air-sealed.  This eliminates drafts, losing heat, and reducing the amount of moisture going through the insulation.  This is why they recommend caulking all light fixtures on the top story of a home.  I am sure that using the paper-backed batts would help create a seal of some sort and offer some R-value, but you would be losing heat through all the little gaps between the joists and the batts.  Would stapling plastic up be possible?
Warmer air is going to rise and make its way to the attic space.  The air under the roof sheathing needs to remain cold, or ice dams is a real concern.  Are you planning on heating this area?  If so, the air leaving the attic space needs a way to be replaced by COLD air, not by pulling warm moist air from below.
I have my garage door and walls insulated, but not the ceiling.  I run a 240 volt heater in it so that I can play my golf simulator in the winters, here in Ohio.  I don't have any issues with moisture on the walls or ceiling and the attic above has soffit vents to allow cold air to get pulled into that space.  I plan on insulating the ceiling as well.
If you run a heater that burns a fuel, it will produce water vapor.  I advise against that.  I find that my garage is 20 degrees warmer than the outside temperature as the heat from the one interior wall migrates into the space.  I would not doubt if insulating the ceiling would add another 10 degrees.
If I were in your position, I would use the paper faced insulation and an electric heater while I worked out.  Just keep an eye on the moisture in the air.  If you have an issue, you will see it condense on the walls or the facing of the insulation.