So!

Today i will show you guys how i play Poppy, and also win with her! :)

But first a little knowledge about myself.

I'm a former CoD4 player who have won Silver and Bronze in several tournaments within the Northen Countrys (Denmark, Norway, Sweden). I was Team Captain on a team called TEXA (Team Exalted) that then converted into a LoL team and failed so hard. So now i'm on my own! :)
Before i started CoD4 i was rolling around Dota Ladder and some HoN Matchmaking (Approx 1750 Rating)

Anyway lets get to the guide shall we!? :)

While other young yordle girls played skip-step and braided wreathes out of posies, Poppy spent her youth earning calluses and grease stains in her father's armor shop. Blomgrun, her father, was Bandle City's finest smith. The only thing he loved as much as his work was his young daughter, Poppy - named for the sprightly sounds of the sparks that leapt from his ever-burning forge. He welled with pride the day she was first able to lift his trusty hammer, Whomper. Poppy immediately took to his art, demonstrating a natural gift for smithing, which Blomgrun honed with devoted instruction.

One day, a Demacian general named Florin Berell commissioned Blomgrun to craft a helm, glorious beyond comparison. Blomgrun toiled away on this project, determined to present Florin with his finest work. He let Poppy set the center jewel, entrusting her with the most important piece. When the pair finished, they departed for Demacia to deliver it in person. Word of the general's order, however, was leaked to the Noxian High Command, and two Noxian assassins were dispatched to intercept the delivery. Blomgrun was able to occupy the assassins long enough for Poppy to escape with the prized helm. She watched helplessly from the brush as her father was slain. Instead of fleeing home, she carried the helm the rest of the way to Demacia alone. She refused payment for it, saying that no amount would compensate for her father's life. Instead, she offered it as a gift, honoring her father's final intentions. Florin saw the grim determination behind the tears in her eyes, and requested that the leadership of Bandle City appoint Poppy as the yordle ambassador to Demacia. Soon after, seeking to crush Noxus with her father's hammer, Poppy volunteered for the League of Legends.

Poppy may be small, but Whomper - or her will - is not.

Passive - Valiant Figther - Any damage dealth to Poppy that exceeds 10% of her current health is reduced by 50% This does not reduce damage from Structures

Q - Devastatin Blow
Poppy Crushes her opponent, dealing attack damage (+60% of AP) plus 20/40/60/80/100 and 8% of her target's maximum health in bonus damage. The bonus damage dealth cannot exceed 75/150/225/300/375

W - Paragon of Demacia
Passive: Upon being hit or attacking an enemy Poppy's armor and damage are increased by 1.5/2/2.5/3/3.5 for 5 seconds. This effect can stack 10 times.
Active: Poppy gains max stack of Paragon of Damacia and her movement speed is increased by 17/19/21/23/25% for 5 seconds.

E - Heroic Charge
Poppy charges at an enemy and carries them for a short distance. The initil impact deals 50/75/100/125/150 (+40% of AP) magic damage. If they collide with terrain, her target takes 75/125/175/225/275 (+40% of AP) magic damage and will be stunned for 1.5 seconds

R(ULTIMATE) - Diplomatic Immunity
For 6 seconds, Poppy is immune to any damage and abilities from enemies other than her target. In addition, Poppy's attacks deal 20/30/40% increased damage to the marked target.

You first question is probably, why do you go for so much Magic Pen? Easy as that, i build Poppy AP. AP Poppy + Deathfire Grasp + Magic Pen = insane DMG. So that's why i build a massive amount of Magic Pen through runes!

My masteries are 9/0/21, Reason?
I like them this way and also works for me :)
I don't really know what is best here, but i guess you can play whatever you want.

For items i prefer the build i linked over.

It doesn't matter what way you buy it. THOUGH! You NEED Sheen as your first item for lane controle! And ofcourse boots :)

I get Quicksilver Sash for situations where it could be used, let me try to build up a situation!

Let's say they have WW as the only "CC" on there team. What you do is you ULT him and hope he will ULT you. What you then do is use Quicksilver Sash to get out and then rape him. That's actually the only reason you can use it :)

A different build i sometimes ride for Poppy is AD combo or more like Attack Speed combo. It works well, but not as good as AP in my opinion.

Rush Sheen then buy Boots. After that you get yourself a Zeal and finish your boots into Berserker greaves. Instantly after this rush yourself 1 or 2 Phantom Dancer and then you get yourself a sweet sweet Triforce!

So thats the end for now!
I will update this as i gather more information about Poppy and my own gameplay!

If you have any questions, ask them below. I will happily answer, btw if you don't think Poppy is useable in Ranked - http://www.youtube.com/watch?v=thvgOjKhGG8 Doublelift Highlights, there is a few Poppy hits in there! Watch them! :)