First specc on Heroic Charge, it's a must for you, then specc on Devastatating Blow and then Paragon of Demacia. Specc on Devastating Blow as often as you can.
Nice Combo Is : First use Paragon of Demacia, then take Diplomatic Immunity, then use Devastating Blow and try to take the enemy into a wall with Heroic Charge.
Good Tip Is : Use heroic Charge as often as you can and try to hit the enemy into a wall.
If follow these instruction you will be Legendary x10 i promise you.
~ Items ~
Regrowth Pendant : It's nice in early game because you don't need to take recall so often and 14 hp every 5 second is nice but you can sell when 15 minutes have passed
Ninja Tabi : You can need Ninja Tabi because it have 23 armor and 11% dodge. Armor it's always nice to a semi tank, and your Paragon of Demacia really helps you on the armor. And Poppy is running 320 without any boots or increased movementy speed for example Zeal or Phantom Dancer. And when you have brought Ninja's Tabi you run 390.
Rod of Ages : Really nice in early game becasue RoA has an bonus cap and every minute you'll get 18 hp, 20 mana and 2 AP. Bonus cap is 270 hp, 300 mana and 30 AP. And buy Catalyst of Protector first.
Rylai's Crystal Scepter : Rylai's Crystal Scepter has hp and AP, perfect for you. And every time you hit an enemy they are getting slowed.
Atma's Impaler : Atma's Impaler has 45 armor and 18% critical strike. And the passive is this : When you are striking an enemy they are gonna lose 2% more damage of your max hp into damage.
Infinity Edge :Infinity Edge, it's perfect for you, 20 % more critical strike, 80 damage and the passive is nice too. You crit 250% more on crits instead of 200%.
Here are two different stuff you can choose from if you have money to spare, what do you want to buy first:
Guinsoo's Rageblade : It's nice for you because it has damage and AP, and every time you hit something you will get attack speed and AP and it stack x8.
The Bloodthirster : Life steal and damage is a good combo on this item. The passive : You'll get 1 damage and 0,25 % per kill, the bonus is lost upon death.
~ Spells ~
Devastating Blow : Your main specc, it's good and powerful and are almost the same as the Q to warwick (Hungering Strike) it takes 8% of the targets hp.
Paragon of Demacia : You only need to specc on it one time, it doesn't make any big change if you specc on it more, just a little bit more movement speed, armor and damage. Use this spell to chase somebody or run away.
Heroic Charge : use your Q and then heroic charge into a wall or something like that, it takes more damage and stuns the target.
Diplomatic Immunity : Use it for teamfights, turret diveing and 1v1. you will get immune to all damage exept the target you have choosen, and you take 40% more damage. On turret dive, the turret would not hurt in 6 seconds.
~ A little story~
One time i played Poppy, i was on team with Kayle, Soraka, Barbarian King (can't spell the name) and Pantheon, we was going to kill the Nexus Obelisk (the turret in the other team's pool). First barbarian King ran in with Undying Rage on,everybody ran in after him, Then we ran out and i ran in with the Ultimate on my self and we all nuked the turret, and when the ultimate where gone, Kayle took her ultimate on me and we did it, we killed the Nexus Obelisk.
This was everything