Hi
As you are likely aware they tended to depict the right eye as it was from th Wedjat or Udjat (first sun deity) that Horus developed from in the pantheon of Egyption worship.
The right eye was somtimes to represent sun god Ra and the left the moon god Tehuti if I recall correctly.
The left eye depeicted the moon so really it depends on what you are seeking to represent
I would suggest checking though as my head is a bit rusty of Egyptian mythology.
The top of the neck or just a bit lower is a good spot.
Take Care
Matthew