gj man on the ap poppy but wouldnt u think of going hybird or sticking a hextec somewhere in there because with ur 'W' ability's active u might do some heavy damage

Except there is no reason for a deathcap if you dont notice poppy is an Ap or Dps Nuke with ap she gets A lich Bane and Guinsoos and shes a nuke already add a rylais and she slows them and nukes them to death no need for a deathcap so i don't understand your down-vote.

I prefer DPS Poppy over AP poppy. and in this case any AP Character (Or build should have a Death Cap.)

Thanks man Much appreciated. i mean you could also get a Rabadons and a deathfire grasp to help but poppy is an amazing champ either or.

Nice build for AP Poppy :)
I have tried AP Poppy sometimes and use a similar build, but honestly I'm just not that good at going AP with her. xD
However, a good job on the build.

Not the full potential. Lich Bane Deathfire Grasp then the rest of your build. DFG is why AP Poppy is so deadly also death cap over rylais 9x out of 10.

The reason i get Armor pen is so that she has a little help when just hitting regular while her skills are on cooldown, i guess you could go either way but i Like the Armor Penetration better.

I like ur build man, but you should take other glyphs instead of magic pen. -CD could be the best option

Why do you take armorpen marks and quints with you, since her q and e does magic damage and those are her main damage sources. On top of that i would suggest adding an 15% CDR item to get 40%CDR.