I bought a cheap mig before I knew how to weld too. Nothing wrong teaching yourself as long as you know your capability and your limits. For something like a rebar bottle tree, go for it. Read, watch videos, and practice on scrap. Don't weld anything where the strength of your weld could be a safety concern for quite some time.
I started on a 135amp northern tool welder, using 100% co2. You can also run flux core if you arent ready for a gas bottle. That welder was "easy" to use, but also easy to use poorly. You can stick a bunch of melted wire on metal easily without penetration. Still, it fit my needs for several years. I bought almost new for $150, sold it 5 years later for the same price. Low risk to learn.
I'm on a Tweco 211i Fabricator now. I researched a lot, it fit my needs well for a good price. I can mig, lift tig, and stick from one machine, and handle 3/8 single pass. Also 120/240V capable. For a home/ hobbyist machine it's very versatile and capable. There are better machines for other people, this one fits my needs very well and I have been happy with it.
I wish my wife wanted something that meant I got to buy a new welder....
Good luck, be safe, and have fun!