Here's my second character. I was wondering whether or not to go with Thief for the luck bonus or Atronach for the hefty magicka bonus and the spell absorption and whether I should go with Marksman for an additional offensive option or Alteration for a defensive option in case things get heated. That, or go with block.

Name: Adol
Race: Dunmer Male Vampire
Birth-sign: ???
Class: Revenant
Specialization: Stealth
Attributes: Speed and Intelligence
Skills: Blade, Alchemy, Destruction, ???, Sneak, Light Armor, and Illusion

Additional questions:

What attributes should I focus on other than luck? On one hand I feel Endurance (HP) and Strength (encumbrance and offensive power) would be best. On the other, Endurance and Intelligence sounds like a decent idea though I'm not sure if not levelling intelligence early on would gimp my total magicka or not (need to check that). The guide recommended Speed, Intelligence, Strength, Endurance and Agility in that order but I am not so sure.

I'm personally a big fan of the Atronach sign. If you do not want that I recommend a sign that comes with bonus endurance. I would also change your favored attributes to endurance and intelligence. it's good to maximize your endurance out of the gate so you can get as much health as you can when you level up. I would not get marksman you would be spreading your skills thin and besides, you have destruction for ranged already.

I have never really paid attention to Luck so your on your own with that.

So, what attributes should I focus on leveling up?

Endurance is almost always good to level up, agility is helpful too (affects how easily and often you are staggered), intelligence, speed if you don't want a horse. as you need it strength and all the others. I mostly level things up as I use it and need it.