I have a cheap Chinese welder that I bought from Harbor Freight for $79, and it welds flawlessly if a flux core welder can weld flawlessly. (Actually, it was supposed to have been on sale for more, but someone screwed up when setting up the price.) I'm on my third spool of wire and haven't had any problems. The complaint with cheap welders is the duty cycle. For what you're doing, a low duty cycle is fine.

Different welders, different guage metal, and technique makes it so that you set the settings at any particular formula. For instance, the low setting on my welder doesn't provide adequate penetration unless you dwindle on the area. I have found that full power and full wire speed is the only way to go. And I control the heat by the speed I move across the area. An auto-dim sheild helps with heat control because you can pull out take a look and plug the mig wire right back into molten metal.

Spend some time practicing on scrap metal of the same guage you will be welding.