Cant really give a great deal of advice but my garage was dot and dabbed with plasterboard, then skimmed with cement before being plastered over, its held up really well in the last 16 years
I dont have an issue with damp but I do have two large radiators in there , one is turned off and the other only on low , I use a electric fan heater if im there for any length of time working
Quite an old pic