[jams]

No expert welder but,

I bought one of the lincoln mig welders (wire feed)it has the ability to use or not use gas. So far I have only used it without. Being a novice my welds are not that pretty but they get the job done.

Wire question:
Without gas you need a different kind of wire, I think it has a flux core to act in place of co2.

I think I bought the welder for 250.00 at lowes and it has paid for itself many times over. You don't think you will use it that often but you will be surprised. It just saved my behind yesterday. I needed a longer drill bit(not sold in stores) so I welded a piee of rod to my drill bit to get the job done.

For limited use you might be able to purchase a small co2 bottle. I think the welds are much cleaner with co2.

With co2 I believe my welder can also weld aluminum. Never tried it.

Thats all from my limited knowledge base.