I'm very new to game developing and still learn the simple and fundamental basics. I followed quite a few tutorials already and haven't found a solution for my specific issue.
Right now I'm working on a tamagochi-like game. As I plan on putting many different pets inside of it I'd like to avoid drawing multiple variations of the same pet to save memory and effort.
Here's the simplified view on the main screen:

To make the Doggo less stale and let it look more alive, I'd like to make him wiggle a bit in his idle state. I'd want to let him sway a bit by rotating.
I set him up as an 2D Sprite node with an AnimationPlayer child node. How do I proceed from here on out?

(In the future I'd like to add animations following those simple steps, like make him jump of happiness after you feed him, let him squeeze downward when you pet or groom him, or rotate him slightly as an eating animation. And I'd like to take those animations over to the other pets.)

The 2D sprite node should probably be a sibling of the animation player node and they should both be parented to perhaps a kinematic body node or a Node2D. Then you can start keying the position, rotation and scale properties of the Sprite2D.

Perhaps share a screenshot of your node tree here so more specific feedback can be offered.