I'll throw in my comments FWIW. I am a hack as well.... I presume you are welding in your floor pans ??? That's tough stuff w/ the dirty, rusty metal....
If this is a 110v welder, I presume it has about 4-5 voltage settings (unlike one of the higher dollar units that have more variability in voltage). Set it at the lowest voltage and w/ a WFS (wire feed speed) of about 2.5. This is a good setting for the thin stuff (to start with) - assuming you're using an 0.023 wire.
I have found that I can get really good, precise tacks by resting the end of the gun nozzle on the metal at about a 10-20 degree angle from vertical. I use about 1/4 - 3/8" of stickout. Squeeze the trigger for about 1 second (or less) - may need to use a rocking motion to get both sides of a butt weld (depending on fitment). You can vary the trigger time obviously as needed.
If the weld bead is high and no penetration, you're too cold. You can add heat to the weld two ways, either turn up the voltage, or turn up the amps by increasing WFS. I would keep it on the lowest voltage and dial in the machine w/ WFS. Once you get the voltage and WFS right, you should have a nice tack w/ similar contour on top and bottom of the metal.
You really need to have minimal gaps between the sheet metal (assuming a butt weld) so you don't blow through....
I have found that at these settings (with solid 0.023 wire and shielding gas at least), a good travel speed is about an inch in 7 seconds (if you want a solid weld....). Don't try to get fancy on the thin stuff by doing circles, C's, etc - just do a straight line weld..... Otherwise you will burn through before you know what hit you.
Ok, I got carried away - MAN I love this stuff !!!!!