Putting is about making an efficient stroke, the same way every time. The goal is not magic. Repeat the good stroke until the subconscious knows how hard to hit the ball. Practice hitting the ball in a straight line, practice hitting the ball solidly. These skill are more useful than making putts on the practice green.
The drill; is to hit four putts without moving your feet.
The first putt is to nowhere but straight. Make a perfect stroke.
Don't look and hit a second putt to the same place by feel.
Look, aim and hit the third ball between the first two, resisting the urge to move your feet.
The fourth ball is hit to the center of the three.