I don't claim to be an expert at Sivir, and people with more experience are more than welcome to tell me how I'm wrong and help me improve the build. The build is unconventional and weird, but if I manage to spark a some sort of cool innovation in a reader that they can use in their own build, then this "guide" (more like random cool thought) was a success.

Here are my reasonings for the choices made in this build:

This is an offensive build, and sivir's abilities fill in the defense. Her passive can get some boosts from ninja tabi, seals, and defensive masteries. That helps cover her from physical attacks, and some points in spell shield and glyphs help cover her from spells. Getting speedy summoner spells mixed with your ultimate's speed boost and dodge speed boost makes you become very slippery and elusive.

Sivir's ricochet costs mana per shot, so if you boost damage rather than attack speed, you'll achieve a lower mana cost for the same amount of damage. Also, Boomerang Blade gets a buff from attack damage, so you essentially get free levels in that skill each time you get a new item.

First and foremost, getting speed boots with dodge helps stop you from feeding early. You still have to play back and avoid early ganks, and use your summoner spells to be as evasive as possible. The lifesteal and additional damage from bloodthirster gives you an important boost so you can accumulate money fast. Finishing up with crits and lifesteal gives you serious firepower late game in team battles. Using your Stark's Fervor and Ultimate in team battles can help turn the tide. If nothing else, your lane partner is happy if they're Twisted Fate or Xin Zhao or Yi or something like that. The lifesteal helps quite a bit.

Personally, I like having a low cooldown on spell shield since having such high hit and run capabilities lets you have it ready every time you engage. I see almost every guide getting more boomerang power, and you could probably buff that for some extra DPS. I personally like keeping the mana cost lower so I can focus items, runes, etc toward DPS instead of fiddling around with stuff like manamune. I see lots of guides say they have mana issues. This build doesn't.