Does adding a ceiling improve temp?
Would adding a ceiling keep my garage at a Warmer temperature for longer?


Yes, but you probably need to at least seal around the doors and perhaps insulate plain metal doors. 


  what is a good and low cost material to use?


In my part of the world, mineral wool in rolls. 

You can suspend this in netting (the upper floor of an office building I use has this, with a false ceiling below, but the insulation is suspended in netting). Stapling some netting to your beams seems to me easier than attaching drywall/plasterboard and laying insulation above that.