Ghost or Flash

I prefer Flash for chasing and escaping possibilities
However Ghost is equally as good

Ignite or Exhaust

I Prefer Ignite because it goes well with Ult Children of the Grave
Double dps as they run screaming then use their ghost to push a tower

Runes are for early game. Period.
Therefore, I chose health marks, armor seals, magic resist glyphs and health quints for a starting bonus of 100 health, 25 armor, 25 magic resist. Helps you survive early game.

Start with
+
Next depending on how long you stay out get

+ OR
Now again, depending on how long you stay out and kills and such next you should finish boots and Warmongers

+
Now you gotta feel how your game is going and what your opponents are building.

Do you need more magic resistance? More Armor? More Killing Power?

Choose one of these 3 to build first


Now typically games end right here but if they don't just assess the game and build correctly.

Once you get Mejai's Soul Stealer you won't need any more Ability power so keep building tank

More Armor items after Thornmail


More Magic Resist items after Force of Nature


If you just need more Health choose one of these items

or even a 2nd
If you want more Ability power (Which I strongly do NOT recommend)

You need to be versatile when playing. So assess the game, see how you need to build.

Everytime you return to base ask yourself

Do you need more Magic Resistance? More Armor? More Killing Power? or more Health?