1stDrive by any chance?
The ideal way is to use the gas, less chance of stalling, easier to get away quicker if needed.
Now, if this is the video I think you're talking about, a big point in that argument with the whole gas vs no gas malarky is Petrol vs Diesel. Specifically, small petrols, the sort you're going to get after passing your test.
- Diesels are very forgiving with the clutch thanks to amount of torque they generate at the low end, most will even happily pull themselves along at idle RPMs without you touching the gas or the clutch pedal (as long as you're already moving a bit)
- Small petrols can be brutal with pure clutch work. Some will behave like a diesel in the sense of no gas (though if you slow down and let the RPMs drop to idle speeds, the car isn't going to pull itself unless you're slipping the clutch), they'll move on the clutch just fine. Some need a bit help, and some outright refuse to do anything without a good boot of the gas pedal.
I mean, strictly speaking, as long as you're in control and not causing danger, it doesn't matter. Personally, I'd use gas in most situations, the only exception would be in stop and go traffic, in which case I'd go on pure clutch work unless the road is too steep. Obviously, if you're going to get moving on the clutch alone (where sensible), make sure the car can actually do it.