Floors and walls in unheated garage/workshop
If the concrete brick block floor is dry you might be able to put a floating floor on it a nice thick pad for insulation the floor needs to be flat. There are many different brands and many snap together, one of the first of these I did back in 2000 is still in good shape and we have had 3 dogs. 
The walls could be covered with furring strips and Sheetrock attached to the strips, then finished and painted. You said no heat so I would not waste $ on insulation. Both projects are DIY for even a new person and a garage is a good space to start and build your skills.