Without any other constraints (like it has to support 1500 lb wagon, etc).
I would use plywood, cut out wheel, spokes & hub as 1 piece, could make two 4 ft diameter wheels from one 4' x 8' sheet.
Then take dowel rod about the diameter of a spoke and cut each in two longways on a table saw (or can cut to spoke length first).
The cut the split dowels the length you need for the spokes, taper the ends if you wish.
Attach to the plywood spokes, to make the visible side of the spokes appear round If you want round spokes.
You can cut another ring w/o hub & spokes for just the outer part of the wheel if you want that to appear thicker.
You can paint on steel bands, or use trim strips if you prefer.
My 1/50 USD