I have a Harbor Freight 90amp flux mig welder. Paid $90 for it. I am completely satisfied with it. It says 3/16" is the max thickness, but I've been able to successfully penetrate into 1/4" when I take the time to do so. For the money, you can't beat it. I've probably passed close to 7 full spools of wire thru it without a single issue. A gas mig welder will make a cleaner weld than flux, but the ease & convenience of flux can't be overstated.
For 1/4" & up, I have a high powered Marquette 220/240v stick welder. I think it'll power up to 295 amps. That thing is no joke; it'll get crazy hot and burn right thru thick plate steel if you don't have it adjusted properly.
The stick welder is nice for when I need the power, but I use the mig welder whenever I can. Once you learn your own successful way to use them, you'll be cruising along. And again, for $90, you can't beat the Harbor Freight one, especially if you only need it for the odd repair or small project like I do.
I can't say it's better or worse than a high dollar Miller or Hobart unit... maybe it's not as fancy ... but it does the job.