I use the cheapest Lincoln mig machine, which works fine and is probably all my circuit breaker can handle. It trips off when I try to do a long bead, so I usually do a series of tack welds. I've had it for about four or five years now and had to replace the inner sleeve once .
There are a few quirks I've gotten used to, like making sure the two buttons that toggle from 1 to 2 are not stuck in between settings, or it won't start. Sometimes I accidentally bump into it and move them from the #2 setting (which I always keep it on). I had a **** of a time before discovering this, after taking everything apart and finding nothing apparently wrong.
I always keep the speed on seven and use the highest setting. Also, since it is not too powerful, I make sure the welds are good enough by going over a spot a few times, which adds more metal and insures good penetration. I' m not so much worried about looks as I am welding strength, and often get ugly looking joints that I can clean up later with a grinder. I used to think a neater looking tack with less metal was fine, until I discovered they often came apart too easily.
It's a very simple machine and I've always been able to keep it running. I only played $75 for it on ebay.