Outermost layer needs to be flame resistant. Stay away from anything nylon as they have a tendency to burn when hit with the flame, slag or sparks.

Carhartt Black Bibs and Jacket – Pretty flame resistant if you’re cutting or welding. Personally I like the Jacket and Bibs better than the jumpsuits due to ease of getting in and out of them (for break) and don’t seem to restrict movement

Layer as necessary - I like the Underarmor Cold as a base layer with wool as a second

Boots – Mickey Mouse or Sorrells