Well, the ol' AC-225 was what I learned on in high school MANY decades ago... One came up on CraigsList a few years ago for $75 and it looked to be in great shape other than the fact that it needed a new front power switch. I just use the circuit breaker to turn it on and off.
I've also got quite a bit of time with and old Lincoln "Pipeliner" SA-200 that we had on the family ranch, but the steel I was welding there was even thicker -- probably 1/4" was the thinnest I ever had to weld on back there.
If I have to do the thin stuff, I can break out the oxy-acetylene tanks and weld (or braze if necessary) it. If it's too thin for me to do with my "skill" with an oxy-acetylene rig, then it's time for some construction adhesive or rivets (which is what I had to do when I was patching some rust spots in the floorboard of my Jeep at one time).
Give me 1/8" wall thickness or better and I'm happy...