I spent 24 years in the home and farm construction business. Here's what I did on my own. I'm in northern Iowa. I made a 30x40x14 heated shop on one end of a 40x75x14 Astro building as follows.
Poured a 5" floor with 8" deep "rodent trench" at the perimiter. Installed 2 drains in the floor by digging a hole 4' deep and setting 18" concrete tiles on end and sloping the concrete to these. They drain all water when washing vehicles. Made steel lids for them.
Installed an insulated 9x7 door on the exterior wall for small vehicle use. Nice thing is my good pickup (4wd) sits inside a nice heated shop all winter, only taken out during snow storms when the old pickup (2wd) can't get through the snow.
I built a 2x6 studded wall on the open end, unsulated and covered both sides with steel.
The posts are 7.5 ft on center, so I laid 2x4's on edge between them 2' on center, secured to posts with joist hangers. Installed R19 kraft faced insulation between 2x4's. Covered with steel. Contrary to belief, you don't need or want a vapor barrier on the outside of the insulation- this will trap any moisture in the wall (not good). The moisture will be on the heated inside of the building, wanting to migrate out to the cold dry air in winter, thus the vapor barrier needs to be on the heated side of the wall, just like a house is built. Tyvek is not a vapor barrier- it's a wind barrier, but is similar to GoreTex that will let moisture through from one side. If you do a good job of insulation installation, you don't need a wind barrier, but to each his own. It (Tyvek)won't hurt anything, if installed the right way (label OUT).
I ran my electrical in the walls before I insulated, and mounted the boxes on the face of the walls. If I had to do it again, I'd put the wiring in conduit on the face of the walls.
For the ceiling, I put 2x4's between the bottom chord of the trusses, 4' on center, secured with joist hangers. I always told my customers use caution doing this, as the truss should be made for a ceiling load, but this building was built 25 years ago, and it's the only one I have with a 14' ceiling. Need that for combine clearance. I installed a 4 mil poly vapor barrier to the ceiling before putting steel on the ceiling.
I then blew 18" of cellulose insulation on top of that, and covered the truss with plywood to seal it up from birds, etc.
I then built a 20x14 sliding door for the end, high density foam insulation, outside covered with steel. This door opens into the unheated portion of the building, so it gets no wind at it unless the big sliding door on the unheated end of the building is open to the outside.
I've had this for 11 years now, and spend most of my time out there. Built most of my gadgets out there during winter- snow pusher for loader tractor, pallet fork for loader tractor, hydraulic tree puller, towed yard and garden cart, and about a thousand other small things, as well as work on farm equipment.
Hope this helps, and sorry about the long post.
I use forced air as a heat source- a used furnace out of a house.
Edit: Forgot to mention, the poly in the ceiling is necessary with cellulose. It keeps the cellulose off the steel. Cellulose contains a salt/sodium that will rust steel if moisture migrates or condenses between the steel and insulation.