ArtMetal

For simply welding armatures together, I'd probably go with a small MIG unit. The learning curve is shorter, they're way faster and easier to do out-of-position welds with than oxy-fuel. They won't, of course, work for heating, brazing or cutting like an O/A rig will, so that may be a consideration.

If you definitely want an O/A rig, I'd get a decent-sized Victor or Smiths setup with at least 80 cu ft cylinders. Anything less and you spend too much time running back and forth to the gas supplier for refills. If you get a cheapo torch setup, you run the risk of getting something that is quickly orphaned when the supplier goes out of business and you can no longer get parts or service.

If you need to economize, check Ebay or try Indiana Oxygen Company for mail order prices that can't be beat. However, if you have a local supplier that has a decent price, get it there so you can get the support later if you need it.