Hi last shed I built for the garden (I stay in a very windy area) 50mm square frame, then osb boards, on top of the boards building paper, then 15mm strapping to allow 12mm shiplap, roof 50 with osb board and two layers of felt, floor rai;way sleepers, 75 *50 then 22mm ply. Shed size 8 by 12 feet, cost around £500 and a couple of weekends work
Shed has never moved, leaked or damp inside, three years later
Least if you make it yourself you can get doors , windows size to suit you, one thing I would suggest if you plan to use as workshop, strengthen the floor where you plan to place machines, this is the only bit you can’t get back to