if you were taught to just pull away on the clutch, your instructor has just taken the easy option, and hasn't taught you to drive, and has only taught you to drive that particular car, and the tosser should be shot.
basically just add some gas, and lift the clutch as you normally would, don't listen to the give it xxx revs, they don't matter really, as long as you give it a bit.
It doesn't matter how much gas you give it, the car might rev a bit, but it'll be the speed that clutch comes up that'll control the speed you take off.
If in doubt, add some more gas, it'll do no harm, well within reason, you don't want to be going foot to the floor too much.
I'm really surprised that any instructor still teaches moving off with just the clutch, I can see the appeal in the early stages of learning, but not later on in the process, I thought that 'method' went out the window with sequential gear changes, i'm even more surprised that an examiner is allowed to pass someone doing it, its dangerous, you take ages to get going, you need to wait for bigger gaps, and you're not 'good to go' so to speak.
Always use gas when pulling off, get in to the habit of it, your driving will seem a lot more positive because of it, just watch how most other drivers drive, they take off pretty sharpish, this is where you need to be.
When you break it down, a stall happens when the clutch plates come together either too quickly or when there isn't enough power to keep them turning, in both cases adding gas will take most of the possibility of stalling away, if you've got the gas on and come off the clutch too fast, you'll be unlikely to stall, you may have a bit of a lumpy start, or a bit of a wheel spin if there's too much gas, but there should in theory be enough power there to keep it turning, and if you come off slowly and have the gas on, the gas will take away any possibility of stalling.
As my instructor drummed in to me, 'GO LIKE YOU MEAN IT' it really does make a world of difference to your driving in pretty much any situation, once you can pull away positively with a bit of speed, everything else like busy roundabouts and junctions etc will become much easier, because you will be able to take the smaller gaps, you will be able to time your merging better etc
Go and practice it somewhere quiet, even a little circuit around a couple of roundabouts and stop every time, and practice pulling away positively and quickly with gas, or even a long empty road, and just stop and pull away over and over again