You are probably going to get mad at me because I didn't pick a Dark Elf and yet I am still posting here. I made a character that I think you could classify as a "ghost." I chose an Argonian for RP and if he gets caught he can activate his Histskin so he doesn't die so easily (I know you said a ghost never gets caught but lets be realistic). I put a LOT of points into Magicka first (up to 200 or so), then slowly built up Health and Stamina, eventually Health overtaking the other two.
(Expert Difficulty)
Conjuration - Bound Bow and Bound Sword are the only weapons he used, no Atronachs or Undead.
Illusion - Muffle, Quiet Casting and eventually Invisibility, no Fear, Fury, or Calm.
Alchemy - No Perks at all, just made Paralysis poisons for sticky situations.
Light Armor - Up to Wind Walker
Sneak - 1/5 in the first, then Backstab and Deadly Aim, but NOT Assassin's Blade.
Archery - Up the left side, ignoring Steady Hand.
One Handed - Armsman, Fighting Stance, Savage Strike.
Bound Weapons worked very well since I ignored Smithing and Enchanting. I pretty much had to use regular weapons until I could get the Bound Bow and actually have enough Magicka to cast it. I found that I could sneak up on anyone in broad daylight with Muffle and Invisibility, when my sneak was in the 50s and I only had 1/5 improved sneak perk. I didn't want to become too overpowered so I didn't take Assassin's Blade, don't use the Dark Brotherhood gloves, don't Smith or Enchant.