You cannot max an ability at level eight!

Rushing Frost Queen's Claim after Sightstone isn't the best item build path to choose as you generally want to build a suitable defensive item depending on the game beforehand (such as Locket of the Iron Solari against heavy poke or Mikael's Blessing against high amount of cc).
Why are there no boots shown in the example build? Why is there no mention of Vision Ward as an essential item?

Reading this and this is recommendable! There is a lot of stuff mentioned in these guides yet be sure to make use of the essential one at least.