First, Edit your build, on the right side above save, publish, view tick Require comment to vote. You'll get a lot of troll votes if you dont tick it.

Consider using [*[name of item,skill,rune etc,etc.]](again without the *) it will show like this: Pyroclasm.
And [*icon=pyroclasm size=55] will look like
Add more intervals, so the text doesn't look like a wall, abuse that Enter button and if it refuses to work use this:
[*center][*color=black]---[/color][/center] (without the *)

Try to organise things where you think it would be best so it would be more pleasing to read, for example items section:
Separate Starting Items/Core Items/Situational Items (Last or special occasion]
And should look something like this
- Write what it will give, how it would help, when to get it etc.

- Adds ctitical chance, attak and movement speed, overall a good item for Twitch, combines well with Infinity Edge and makes you even more mobile.

Dont forget to use Bold, Underline and color to point out important things.
Abuse the Enter button so the guide won't look like a wall of text.