This build and guide is absolutely horrible. I suggest looking into other builds before trying to make your own. You should not try to make a build when you aren't even level 30.

I will start with your runes... They are completely wrong. They should be something like this.
Marks - 9 Greater Mark of Desolation
Seals - 9 Greater Seal of Evasion
Glyphs - 9 Greater Glyph of Focus
Quint - 3 Greater Quint of Evasion

Now to speak on your ability list.

Get all 3 abilities with your first 3 levels then other than level 6, 11, and 16 for your ulti you should max out empower first then leap then counter strike.
I say this because the empower gives you a 40% bonus damage from both AD and AP.

Purchase order is wrong as well. The only two items you have on your list that are right are Ninja Tabi and Guinsoo's.

Your spec is almost right.

I suggest you look at my build ( It is not a guide, Just a build and spec and purchase order ).

Please comment! I need your suggestions .