The clutch is the key to control.
This is the most important point and can't be emphasized enough.
In a car with an automatic transmission, you are used to the controlling launch and speed with the throttle only, because the auto transmission provides the slip, and allows the smooth transition of power to movement.
On a bike, you have to manually provide that smooth transition by feathering, or slipping, or gradually engaging the clutch. The throttle becomes completely secondary, and the main requirement is that you provide enough throttle not to stall. There is no real disadvantage to providing more throttle than needed, or racing the engine, as long as you are still controlling the clutch. The throttle can be wide open, and the bike will still not move until you engage the clutch, and you can still start very slowly even with the throttle wide open. Now that is an extreme case, but it is much more preferable to have too much throttle, and control launch speed with the clutch, than to have too little throttle, and stall the engine.
Just keep controlling the clutch during launch until you have the speed and throttle matched, and you are well underway. Most newbies try to engage the clutch too quickly, and seem to want to get it completely engaged as soon as possible. Have patience. Just keep feathering it until you are sure that you're smoothly underway, and you will have no problems.
Practice barely getting the bike to start to try to roll, and then getting it to stop trying to roll by using the clutch only, without ever letting the clutch completely out or pulling it completely in, and you will quickly develop a feel for the engagement point.