Bob Engelhardt writes:

As the others have said, or referenced, the welder will require 50A
*at its maximum output* (225A). I don't think in 20 years that I have
ever run mine at more than 125A. So if I were adding an outlet in the
garage, say, I would run a 30A circuit just because I could use 10 ga
wire iso 6(?) ga. Cheaper and much easier to handle.

Wire the outlet for the rated maximum of what you're going to plug
into it. Don't put in an inadequate circuit, planning to never turn
the welder up all the way.