Launch, and 1st-2nd are the hardest for everyone learning. They are the highest torque, and require the most delicate left foot.
Try stepping up the parking lot practice. See how quickly yet smoothly you can let out the clutch without stalling at idle. being smooth in that trasition is what you are trying to learn. Anybody can do it super slow without stalling, but you don't want to do that at a stop light, or on the first to second shift.
You can bring the RPMs up a couple hundred to start with to build confidence, but doing it as quick and smooth at idle without stalling is the key. Turning on the AC/defrost may bump the idle by 200RPM or so without you having to do it with your right foot.
By the way, once you learn all this, you will have to teach your left foot a whole new lesson if you want to learn to left foot brake...
That is much harder IMHO.