I'm mostly a self taught welder. I weld something damn near every week mostly for personal projects. I bought the Lincoln 180 (220v machine) and did flux core for my first projects. The shielding gas makes welding so much better. I knew when I started I'd stick with it long term though so adding an extra $400-500 to the machine was less of an issue. Haven't used a Harbor Freight welder, but some of the tools I've used from them like angle grinders and a plasma cutter a buddy bought, make the projects less fun. If the OP is convinced he will stick with it, I might suggest going ahead and paying a little more to get a good machine. I recently bought a miller engine drive for a project I worked on and I love that thing. But $7k for a welder and a way to transport it probably isn't what the OP is looking for.

The one thing I will stress beyond anything else is safety. Welding in tennis shoes is a bad idea. Slag melts the shoe and goes between your toes. shite goes really bad really fast with an angle grinder if you don't know what you're doing. This is where having someone show you how to properly cut metal comes in handy. I know a professional welder that severed his thumb with an angle grinder grabbing. He was a pipeline welder and started his own outfit. I've laid my arm down in a fresh weld and that isn't pleasant. I've been cutting metal only to look up and see that my sparks were aimed at a gas can. I've had cutting disks blow up in my face without safety glasses on. I've been very fortunate that I haven't been severely injured with some of this but I take note of what happened when something goes wrong and really make sure I don't make the same mistake twice.

You spend more time with prep work than you do actually welding. I know it's been mentioned a few times here, but the tighter you can make your cuts, the better off you're going to be. Cutting is equally and arguably more important than the weld in many cases. My goal is generally to get my cuts with 1/16" of where I'm going with it. Doesn't always happen. Learn to mark in a way that you can cut the line extremely straight. Having an extremely flat surface is one of the best tools you'll ever make yourself. I use my welding table on damn near every project including woodworking. You also can never have enough clamps.