I took a welding class at a local vocational school-- it was terrible because the instructor didn't care about the students progress. The class taught me what a welding machine looked like and where the tungsten goes and what an argon tank looked like, but that's about it.

Then I bought a book by Larry Jeffus: Welding Principles and Applications. I read it cover to cover and learned a lot of academic information about welding. I could pass written exams on welding, but wasn't very good at actually welding anything.

Then I bought a Lincoln Invertec V205 (similar to the Miller Dyn 200). A billion pieces of scrap aluminum later and my welds are decent these days. People who TIG for a living can definitely make prettier welds than I do, but my welds are plenty strong and pretty enough for my needs. But there is always more to learn and a better weld to strive for.

So I am 90% self-taught. Today I fabricate dozens of custom motorcycle racing parts for my race bikes, race trailer, etc. I trust my life with my aluminum TIG welds on my bikes.