Make sure you wait at LEAST 10 seconds after the all clear to go Green flashes without any Red flashes to ensure you have 6+ satellites (the longer, the more satellites, the better), and MAKE SURE YOU ARE IN GPS MODE for liftoff.
I see too many guyes place their Phantom facing into wind, then standing behind the pahntom (downwind), launching in ATTI mode and not GPS ATTI. The Phantom will drift backwards and if the legs are dragging across the ground, it will tilt over.
Its a good reason to keep the prop-guards on until you have mastered the kift-off technique... see below.
As you add weight to your Phantom, you need to increase the attitude gains to compensate for the extra inertia.
Mine are at 250% and flying perfectly with gimbal, gopro, VTX, iOSD, propguards, LED striplights, LED headlight, Low battery Audio alarm, and a few extras.