Hi again

When the car is stationary on neutral... there's no sound just the engine revs.
It's from the gearbox for sure.When the clutch pedal is pressed there's no sound.
When i released the clutch when it contacts i heard something like a "click" then it rattles a bit and goes away as i speed up .
On first and second there's a slight rattle up to 1500 RPMs or so.
At first i thought that it's the release bearing but I wanted your opinion.