Thank you so much for the tips guys.
Next weekend I will try every tip to see if I find something better than my current solution (where I have the skin border around the eye).
Initially, I remember to try use the clipping, but I gave up because I couldn't use one for each Eye. I also remember to try create just one for the 2 Eyes, but I can't remember now the why I gave up.
So I will give it another chance 😃
@Update about this...
I was investigating more about the border issue, and I ended up finding the solution when I was trying to solve the warning on Unity's Console that was asking to reexport the spine project without Premultiply Alpha.
So I was reading about it and just realized that we can use the Sprite Shader on Skeleton materials:
spine-unity Export Settings: Texture Packer Settings for spine unity
So, I am so happy with that result and will not make use of clipping in this project. 🙂
I really appreciate your help, guys.