Boots of swiftness are definitely a top choice on poppy as she has to be close to do damage. I feel that with boots of mobility your movement speed is impaired as you always have to be close to deal damage. If the team is high in Crowd controlling effects, then I suggest mercury treads at start than than boots of swiftness. Obviously since poppy is being played as mainly a capturer, your second choice of item will be Priscilla's Blessing. This item is great for poppy because stacked with Paragon of Demacia, Poppy can hit speeds well over 500. This item has another great bonus because of it's 15% capture rate increase; self explanatory. Next grab a sheen. Poppy is moving fast and dealing decent damage, but once you grab this, hiting squishy champions for a chunk of life with Devastating Blow will come easily. Warmogs is a great choice for any player playing the role of a capturer because being able to take a bit of damage, running across the map and capturing another point is imperative to this role. Lich bane after warmogs is an excellent choice for poppy because it gives more movement speed, mana, a great unique, and more magic resistance. By the time you get lich bane you should already find yourself with a killing spree at least. Grabbing a Deathcap just makes killing champions EASY. If you can effectively ace the team because you are spamming your Q for 600-1000 damage every few seconds, you can certainly capture at least 4 turrets and win very fast.