My .02
As big as you have money for and the city build permits will not be a major hassle.
My friend helped a previous co-worker erected a 40 X100 steel shop, then that guy helped my friend errect a 40 x 60' (16' high side walls) building on his country property.
After moving his tools, projects in as getting started on one project, I said to me he wished he had built at least 40 x 100' also.
Planning where to add sheds, overhangs buildings to make up his storages, He also already had a 2-1/2 car garage.
He's retired, 2 yrs. and 64+ years old, too young to quit- he's just getting stated on the things he wanted to do for years.
So! ?? What do you really need? At a minimum to do what you want. Not time to slow down if you can. TOTTALLY respect you will and enthusium!
Best,
Doug