I main Sion at the moment. The ghostblade helped me a lot. My opinion on Sion is: Farm like a ****** and don´t try to help your team in every situation. You want the farm and probably end up with 700+ on your passive.

I usually build hydra after golem, boots and ghostblade. At that point (next to your tankyness) you´ll become and assasin and pop nearly every ap/ad carry (even when they are fed). After that I´ll go frozen heart or warmogs (depends on my lead) and one last ad item.

I tried many ad items, but none works as good as the ghostblade. Thanks again for the awesome suggestion

Thank you for the suggestion, I will try the zeal on Sion as soon as possible :)

Looks like a very promising build. The item I would want to incorporate into this build would be a dagger and the item it builds into, zeal. I always use it along with the Hydra and it always makes for a strong Sion.