What I am doing wrong for smooth shifts?

[pothole]

Without observing you, this is hard to answer.

If you are changing gears reasonably rapidly, you don't really need to "give more gas". Indeed, you lift of the gas you depress the clutch and only get back on the gas after you have selected the new gear and re-engaged the clutch - well, in reality you're getting back on the gas in parallel with re-engaging the clutch, but anyway.

This applies to changing up through the box becuase when you select a higher gear, naturally the revs will be lower in the new gear.

Downshifts are a whole different ball game as the revs are higher after a downshift and you need to blip thr throttle and /or use heel and toe if you are braking at the same time. But that's getting ahead of ourselves.

Getting back on message, if you spend too long changing gear, obviously the revs will drop. The solution for upshifts is not to "get on the gas more" or to blip the throttle, it's to speed up your gear changes.