welders?

right now the navys putting me through welding school. weve learned axy-acetylene cutting and brazing so far. right now were in the process of sma welding, and next we learn gta welding. how different is mig then gta and sma. i know the equip is different but is the concept the same. aslo when i reenlist in sept i want to buy a welder. i plan on using it mainly for some frame work on my truck as well as body work. what welder do you reccomend? any help is great thanks.