I am not feeling great about the proportions, color, contrasts, and shading... any feedback will be appreciated!

I think this is good for your first portrait! Hopefully the diagram makes sense. With pixel art, if the colors seem wrong it can make the proportions feel wrong.

In the diagram I made (pls excuse my garbage lettering) I tried to show you what I meant before. Instead of making shades out of yellow getting darker to black, I took yellow getting darker but in a red/brown direction.

So instead of the sort of desaturated/ickish you get a more vibrant blonde for the hair. I think the hair pieces just need a bit of cleaned up too.

For the face, I didn't think your pallete needed changing. You have good darks but didn't use it much. I also took one of the semi-darker shades and added some AA to the nose/lips and general shaded side of the face. Don't be afraid to be bold! All it needs in my opinion was a bit of contrast.

Hopefully this was helpful!