Amazing how cheap it is to build a shell isn't it?
The big costs of building a house come after it already looks like a house, appliances, flooring, electric and plumbing, fixtures, all add up.
A garage is a much simpler and cheaper project.
Don't have much to add, bigger is better, insulation and heat is always nice if you're going to be working out there a lot. The construction details vary depending on region and climate. I prefer wood buildings and steel roofs, wood makes alteration, insulation, etc a lot easier. Scissor trusses give you more headroom and don't really cost any more. I wouldn't even consider vynil siding unless that's what I had on the house, I really like board and batt on outbuildings, or T111 for fast and cheap.
A set of used or scratch/dent kitchen cabinets can make a nice addition to a shop. Lighting is also important, lots of outlets, a 220 circuit, maybe a pit. Nice to have an overhead hose reel too for air.
I've used a woodstove in my shop for many years, but I did have one sawdust flash early on, be careful of that. I've heard of dust explosions that actually damaged the building severely.