I'm a quite new player with around 600 games during last couple of years and currently playing in Silver so most of you probably don't care / already know better =)

but nevertheless

This is meant to be a very short guide merely to emphasize the power of Runaan's symbiosis with Statikk Shiv and Miss Fortune's Impure Shots for maximized carry potential. This is most likely not a new idea and I don't claim to have invented it, but I haven't seen any MF building a Runaan's + Statikk...ever. So I'll share the basics with you.

Miss Fortune (MF) is strongest when not being the first focus of attention in fights, and allowed a tiny bit of time to deal damage. That's why we focus on heavy AOE bursts of magic damage accompanied with high criticals of physical damage and of course, high attack speed.

The strength of this build is not building armor reduction, but combining magic and physical, which most AD carries cannot do as succesfully.

MF can deal quick hits with Make It Rain coupled with some autoattacks or take out the entire team with Impure Shots and Statikk if not quickly focused on.

This build can also be used to play top lane (pick teleport over heal) against some ranged champions, if your team needs or especially wants it.

ITEM and WHY

Infinity Edge: a no-brainer for any AD. First big item (even before boots if situation allows).

Runaan's Hurricane: Allows MF's passive (W) to hit up to 3 targets and boosts her attack speed. A good item to have if you decide to want more on-hit properties from other items.

Statikk Shiv: Further increased attack speed with aoe chain lightning that can crit.

Note: Runaan's triple attack reloads Statikk quickly, which allows super quick magic bursts. This in addition to already quickly-lethal Impure Shots help finish the job.

You can build whatever big items outside this core. With the core you are around 2 attacks / second (without W), 40% crit and around 200 attack damage. For items there are two slots remaining. Good choices are anything that increase your survivability. Guardian Angel with Frozen Mallet, or two Bloodthirsters if you wish.

Test the core and see if it helps you to carry and win more games.