To me, tank is the best way to use Poppy.

Best build for tank Poppy is: sunfire X1, dodge boots X1, randius omens X1, Thornmail X1, Warmog’s/Force of Nature(depending on who your versing,) and Warmog’s/Guardian Angel.

Best is to use W, E, Q and W,E,Q again.

Poppy is best for ganks in Summoner’s Rift when she initiates the attack as she has her ulti (R) to make only one person available for attacks.

Best build for Ap Poppy is: Lich’s Bane, zhoyna’s Ring, magic penetration boots, void staff, Archangel’s staff, and guardian angel.

Best build for Dps Poppy is: Blood Thirster, Beserker greaves, 2 phantom dances, maldreds blood razors, and sword of divine.

Poppy is one of the best heros for hybriding as well.

You can get tank and ap as well as dps and ap.