We use MIG welders at uni.
Very easy to use, can pick it up in a few days i rekon, even less that that!
If its a good finish your after though, you might be best getting good at rod welding.
Alot harder to pick up, but if you get it right, then the end results can be spot on
Personally i'd go for a MIG welder, easy, clean, and handy to work with.
Think the gas used is "argon", with a 25% C02 mix, most specialist toolshops will have some, the sizes vary. If you get serious though, different gases perform better on different metals.