Not OP, but I learned MIG at my local community college about 15 years ago. It was mostly pipe-fitters getting certified in the class and I was able work on whatever projects I wanted. I started with stick, then went to MIG, and then did a follow on class where I told them I just wanted to do Oxy-Ace. I think now they offer a more variety of classes, for people who want to do art and such.

If I recall, flux core is dirtier, and having a tank of argon on your cart isn't too expensive for a shielding gas. I lived in a studio and luckily my neighbors were cool with me running a chops saw.

I have that same problem, too.

I got a cheap stick welder and some plate and played around until I could kinda do it. Then I fixed my mailbox. It looks horrible, but it doesn't move anymore.

Most MIG machines can run flux-core wire without any problems. Gas-shielded welding (MIG/TIG) produces cleaner welds with less slag that needs to be cleaned off, but doesn't work outside with any wind.

Depending on your location, you may have a local makerspace, tool library, or similar; oftentimes places like that will have beginner classes on the cheap. Granted, that may all be on hold presently for Covid-19, but could be a nice thing to bookmark for later.

Edit: as an example from my own locale, the Denver (Colorado, USA) Tool Library typically has a beginner's welding class for $150: https://denvertoollibrary.org/upcoming/welding-101-fjbkt-k4g..., though they've suspended all in-person classes while the pandemic rages.

Flux core is really useful if you either don't have the ability to use gas, or are working outdoors in the wind.

Our shop is indoors, and we have nice machines.