Do you have access to firewood? Or trees/limbs that you can cut into firewood?
Try Cordwood Construction. Instead of stacking up rock for your walls, you stack up pieces of firewood - with a little mortar along each end to tie them together. Cutting your wood to about 16 inch lengths makes a pretty good wall for one story. And the finished wall looks a lot like stone. Round sections look like large round rocks, split sections look like more random rocks.
There are a number of books out there on building with "cordwood". Mother Earth News, Farmstead, Backwoods Home, Backwoodsman, and Harrowsmith magazines did several articles on it. Some people use it to fill in on a standard post-n-beam framework, while other use it as the complete structure and support for the roof. And the method of construction goes all the way back into the late 1800's.
Several people I know laid down several railroad ties for a 3-sided "foundation". They then started stacking up their firewood - using mortor along each edge to hold each piece of firewood in place. At the corners, they alternated stacking each layer of extra long pieces of wood - to help tie both walls together. Rough window frames were nailed together and set in place as they built the walls up. They stacked them up to 8 feet high at the front - sloping down towards the back at 6 feet high. They then put a couple 2x6's across and nailed on some roofing tin. Two days of semi-light work and they had a shed to park their car in. The only problem they have had is a slight shifting of the walls as the ground has frozen/thawed and settled. Nothing major. They now want to put two large swinging doors on the front to be able to close it up for more secure storage. And make another to use as a shop.
A Cord of firewood is a stack 8 feet long by 4 feet wide by 4 feet high. With wood cut to 16 inch lengths, that makes three stacks of wood 4 feet high by 8 feet long. So some simple calculations will give you the amount of firewood you would need for the size shop building you are interested in making.
So do a little web surfing for "cordwood construction". It might be a good option for you.
Mikey - yee ol' grumpy blacksmith out in the Hinterlands