I think that regardless of the machine you have or have access to, being proficient in using the tool will make a world of difference. A $4000 tig may be the cats pajamas for doing bodywork, but if you don't know how to use it, you have a $4000 box to trip over in the shop.
I'd say get some scrap, use the machine you have, and practice, practice, practice. Making sure the metal is clean (no paint, no rust, no contaminants) will help a ton as well.
