As I couldn't definitely get rid of vibrations and jello with other solutions (earplugs, moongel, etc), I bought the Tarot T-2D gimbal, also because a camera stabilization system is the only way to go for having good quality aerial (and not aerial) videos.
Comparing this video with my previous tests, the gimbal really makes a huge difference. It makes THE difference. When I saw the video, I was impressed with the results (although they can be much better!), I didn't have to modify the gimbal settings at all, it worked out of the box. I use a 500mAh 3S 20C for the gimbal, lasting around 1h30m.
In one hand I've improved video quality, but on the other hand I've added too much weight to the quad (gimbal + stuff to hold it + gimbal battery + landing gear), going up to 1.7kg, which is a lot, probably for the type of motors and of course for the simple plastic propellers (a few times they broke in the air because of the weight!).
Setup:
Frame Whirlwind FY450
BL-2830/11 1000kv rotors
20A SK ESC
10x4.5 Plastic HK propellers
KK2 controller board
GoPro H3 black, 1080x60, N FOV
3300mAh 3S 20C battery
Turnigy 9XR transmitter
FrSKY V8FR-II receiver
Fatshark FPV camera
Fatshark Predator goggles
ImmersionRC 600mw Tx
1000mAh 3S 20C battery for video Tx
Gimbal Tarot T-2D
500mAh 3S 20C battery for gimbal
Plastic landing gear