I have a house in Houston with drywall already installed on all 4 walls of a 2-car 22'*25' garage. Two walls are shared with conditioned space and insulated. One SW facing wall has no insulation, and the NW facing wall is 90% insulated garage door, the remainder uninsulated.
The uninsulated SW wall (afternoon Texas sun) actually protrudes into the conditioned house, so only about 15' are uninsulated. The garage ceiling is not currently insulated.
My goal is to make the garage a little cooler in the summer and a little warmer in the winter. I do not plan to add HVAC.