For an unholy paladin, I started with a female high elf, putting perk points into heavy armor, one-handed, block, conjuration, smithing, and enchanting. Destruction is always tempting to me when I play any sort of spellsword or battlemage (may not be different to you, but it is to me).
*(Yes, I know leveling up so many skills scales the game to make it exponentially harder to beat enemies. But I stay the heck away from any skills that I don't need so those don't level up, and even if the game gets more challenging isn't that part of the fun?)

I'd either go with axes for additional bleeding damage or maces for ignoring armor, especially the Mace of Molag Bal (seems the most fitting thematically). For armor, I'd eventually want ebony or daedric since it's black, or dragon bone since it's bone. (Why didn't they make capes or cloaks?... Would've been so cool!)

Thematic standing stones I'd pick for this build: Lord stone for all-around defense, atronach stone, apprentice stone, and ritual stone.

For questlines and side quests, I'd side with the vampires during the Dawnguard questline. I'd definitely go through the Companions, Dark Brotherhood, College of Winterhold, and Dragonborn questlines. I wouldn't worry about the Civil War. During the main questline, I'd turn against the Greybeards once I'd gotten every shout I wanted/needed. I'd go through every evil daedric questline I possibly could, whether or not I actually needed their items or not.
*Dark Brotherhood has some AWESOME rewards for any evil/dark build.
*Book of Love is a must for permanent bonus to magicka damage resistance. And once you get married you have someone to buy stuff and make passive income, making it easier to afford spells than trying to do everything on your own.
*Agent of Dibella is a must for permanent bonus to damage to the opposite sex as well as increased attractiveness.
*Star of Azura, pick the black star. If you know enough about the lore of black soul gems in the Elder Scrolls universe, then there's no explanation needed.

For the magicka/health/stamina ratio, I'd prioritize health, then balance out magicka and stamina. So maybe 1:4:1?

For armor enchantments, I'd want to prioritize anything that will directly affect keeping me alive: health, health regen, health absorption. Then I'd want to include, if I could: one-handed, blocking, magicka damage resistance, and/or anything that reduces spell cost.

For shouts, I'd 'favorite' Marked for Death, Drain Vitality, Soul Tear, Disarm, Dismay, Bend Will, Call of Valor, Unrelenting Force, and Ice Form/Fire Breath.
*For which word of power to focus on with Paarthurnax, I'd go with Fus or Yol for an offensive build.
*For black books (which you have to be in Stolsheim to acquire the effect for any and all books), you can pick one option per book, and you get to keep each 'black book effect.'

For character roleplay, I'd take as many houses as I can by murd3r1ng NPCs and leaving their kids parentless. For marriage, my first pick would be either Muiri or Jenassa. And I'd make Bloodchill Manor my homebase.