Ford

Well if its a manual which it sounds like, in first gear you either have to also have foot on the clutch so it does not die if not rolling to a stop or giving it the gas to speed up if your stopping your putting your foot on the clutch or going to neutral, so it does not die. It can not idle in gear, understand.

I have my foot on the clutch, and when I put it into first gear it cuts off, unless I have my foot on the gas pedal and I rev it a little

May be your neutral safety switch.

Sounds like your ranger is bucking , mine did same thing but in 3rd gear got to the point where it started doing it in 1st , 2nd & 3rd it was the cam shaft synranizer it looks like the distributor , my 2002 3 liter 5 speed doesn't have a distributor it has a cam shaft sycronizer my truck never ran as good as it does now