For 75/25 gas mixture, it sounds like you're in short circuit transfer mode, so your shielding gas should be somewhere around 25 cfh. For 3/16" to 1/4" thick steel using a #0 cutting tip, your settings should be about 30 psi for oxygen, and about 4 psi for acetylene. At 12 psi for oxygen, you probably had trouble blowing through the edge of the material to get your cut started. You should set your oxygen and acetylene gages after you light the torch and with the trigger pulled, because that is your actual cutting pressure. Also, make sure your cutting tip is clean, especially the oxygen orifice in the center.

Hey Friend,
Gas flow should be around 20cfh for most GMAW, it depends on the size of nozzle, wire extention, process/metal transfer, and shop conditions.

Putting aside the manufacture of the oxy-fuel equipment, due to torch and tip styles varying of course (4 hole or 6 hole,and of course tip size), I'll give you my two cents worth on the subject.

It's not so much the pressure settings as the condition of the cutting stream (center orfice)that makes the difference. Even new regulators may be out by as much as 5psi.

Setting to high an oxygen pressure creates more problems as well as wastes oxygen.
So concidering that most set the oxygen pressure too high 30psi and up, you are maybe just a tad low on the oxygen at 12psi, but with a clean tip/cutting stream it will still work on thinner materials, guage to about 1/4inch.

Picture a group of people trying to exit through a small opening...single file works better then a mad rush.

So tips/ cutting streams clean up by reducing oxygen pressure which has me to think excess pressure causes a turbulance and restriction of the Oxygen stream in the tip ( the door story above).

The gas pressures should be set at 3 to 5psi for Acetylene, and 20 to 30psi for the oxygen, but when you squeeze the oxygen lever after the initial flame adjustment of the preheat flames to neutral just to a point where the feather disappears,the oxygen cutting stream should be visible and at least 4 inches in length of longer. If not the tip is either dirty, or the orfice is enlarged/tapered and the velocity is lost which will fail to properly oxidize and eliminate the slag resulting in a chewy cut,with poor slag removal.

I have used a varity of torch types and styles over the years and while I would advocate to always follow the manufactures set up procedures, the secret to good cutting is not so much the pressure of the oxygen, but the quality of the cutting stream being #1, preheat on the back side of the material to be cut (thicker materials 1/2 and up only) #2., proper support of the torch #3 and finally smooth and steady cutting speed #4.
Try to sweep across making the cut rather then the drag/pull/push the torch forward or back.
Good luck and I hope my two cents was well spent.