Anything works well on these. My dad had a Harbor Freight flux-core welder still in the box he bought a long time ago and never opened. We stopped by there on our way to the Grand Canyon and noticed that the carrier I put my motorcycle on was splitting. I took the $100 welder out of the box, set it up, and fixed the carrier in about 40 minutes. All the little flux core machines are the same, if you don't get a name brand. I have a big Mig and a big stick, Hobart, but his little flux welder was so easy to use, I bought one of those when I got back. I wouldn't pay more than around $100 for a little wire-fed welder. If you aren't going to use gas, don't buy the capability. The wire fed only cable is much more flexible--you can tie it in a knot and it will still feed. As long as all you are doing is steel, just get the flux core, and get the cheap one. The wire size is the same so you aren't doing 1/4" in one pass with a 130amp or whatever with the same size wire. I use the little wire-fed for small things and the stick welder for everything else.
I really recommend getting a stick welder to start with. Those little wire-feds make really nice welds, but often the weld is sitting pretty on top of the work with little penetration. Once the arc is working, you tend to start moving. But that tiny wire and low amps means it's easy to get the arc working, but it isn't going down through the metal very far. Anything that requires strength, I use the 230amp stick on. Really, I only use the wire on very thin stuff. Exhaust pipe and sheet metal. The wire welder needs the metal absolutely clean and uniform because it comes out at a set rate. The stick you can leave in to heat it up and pull back a touch when you need to--much more control. You need the wore feed for thin stuff, but I sometimes use 1/16th rods with the stick and I can weld coffee cans together--or I have, but coffee comes in plastic these days.
If you are building bumpers and welding spring pads and such, you need a 200amp stick. If you are doing work on the body and putting wings back on the yard flamingo, you need the little wire feed.