As AD Sion, early game is not his specialty. As Sion you should be farming minions until you have your Phantom Dancer and your Berserker's Greaves. 10 min in the game you should have at least 20-75 minion kills. After you get these two items you are ready to slice your prey.

In middle game your should have 2 Phantom Dancers, Berserker's Greaves and your Vampiric Scepter. Also you should have 75-125 minion kills. When ever there is a wave of minions, you should always be the first one there farming them.

Late game you should have 2 Phantom Dancers, a Berserker's Greaves, a Blood Thirster and a Infinity Edge, at 20 minutes. Late game you should have 125 and more minion kills.If not You should try staying out of trouble of fighting and look for minions to kill. At 25 min you should have Sword of the Divine or Atma's Impaler for your last item.

The reason for farming as Sion is because of his E ability Enrage. This ability helps Sion late game due to the amount of health he will gain from Farming. Late game, even without tanking items, Sion could still be the off-tank, from just killing minions.

Both of these items depend on your Early Game. If doing great on minion kills and have over 2,000 HP than the better choice would be getting the Atma's Impaler for more crit. Even though you are losing more attack speed by getting the Atma's you are still becoming stronger from the crit. Sword of the Divine would be a better choice if you are feeding, or not getting enough minion kills that you need for your HP.

Prior to the creation of the League of Legends, the city-states of Demacia and Noxus were locked in a brutal series of on-again-off-again wars that spanned the course of centuries. Both powers sought an advantage over the other, but Noxus was the city-state willing to forego conventional morality to achieve its goals. Only brute strength and the will to use it mattered to Noxus, and this is best exemplified in the murderous warrior, Sion. Used by the Noxians as a human battering ram, Sion would be sent thundering ahead of Noxian troops. He would mercilessly slaughter foes with his large double-bladed axe, ''Chopper''. His complete disregard for caution ultimately cost him his life, as he was captured and summarily executed by Demacian forces.

The Demacians thought that the beheading of Sion would be the end of his bloodthirsty ways. Death, however, was merely the beginning of Sion's rise to power. The famed Noxian assassin, Katarina, recovered Sion's remains and Noxian necromancers reanimated the behemoth to serve Noxus once again. Sion's reanimation actually bestowed new powers on him and increased the potency of his existing abilities, making him even more of a terror to behold on the battlefield. The Noxian High Command had a powerful new weapon in their hands - one they have brought to bear as a champion in the League of Legends. Even though Sion's increased powers would make him a powerful tool for the High Command's use outside the Fields of Justice, Noxus no longer risks losing one of their greatest champions in the League to chance or circumstance; Sion's days as a front-line fighter for Noxus' military conquests are at an end.

"For Noxus, death is a promotion." -- Pantheon