Hi am scottishsteele and this is my first build. Now Sion is one of my manes and has been for a long time he is just so fun to play. This build will show you the true way to play Sion and that's AD. The reasons for this is that once your shield is gone you're not doing any damage also going AP is wasting your ult and you don't want to do that now do you ?
If you want to play Sion AP plz just go away and don't look at my build. But if you are a true AD King then read on.

Pros
+ // Gets Very tanky with his E Passive
+ // Ulti will turn a team fight.
+ // Can Solo Baron/Dragon easily.
+ // Has a Good Mid, and especially Late game.
+// Strong lane presence - He can soak up damage, has a high burst, can indirectly heal allies, has a stun and a high base damage.

Cons
- // Focused hard with CC.
- // No natural escape mechanic.
-// Keeping his E active hurts you as well, so last-hitting is a must with him.

For my Masteries I go 23 in Offence 2 in Defence and 3 in Utility the reason for 21 in Offence is that the extra damage helps you out early game. The 3 in Utility is so that if you do die you are not sitting there for to long.

When I pick runes I think about early game so what would be best for Sion early game? HP that's what would be best so I pick Greater quintessence of fortitude which just give you tones of HP for early game. Next is some more HP for early game so I pick Greater seal of fortitude now that we have a bit more HP for early game 126 to be precise. I will start to get some attack speed as hiting more is good so lets go for Greater mark of alacrity. Then last but not least we will get some cooldown reduction so we can stun more so for that lets get Greater glyph of focus.

Now for the farming advice I am going to give you is to last hit with E as it has an amazing passive if you don't have 250 extra HP with it by late game then you can not last hit LOL

Now we are at the good part you will want to start with a long sword and a HP pot this should give you about 108 AD to start with which is great if you do what I tell You and get E first and the HP pot lets you out last them in lane. When you go back for the first time you should have the money for a Brutalzer and a HP pot the HP pot is for when you get ignite put on you if you pop your HP pot at the right time it should save you. On your second time back you should have money for a phage and boots if you don't then just ping dragon till you team do it LOL. Next should be your boots of swiftness and a BF sword.Then as soon as you can turn your phage in to a frozen mallet this will give you a slow so they can not get away now. Then after that turn your BF sword in to a bloodthirster. Then you will build a infinity edge and your last item should be the Atma's impaler so that you can turn that sweet HP in to sweet AD.( a build should depend on who you are fighting at the time so you may need to swap some items about. ) PS don't forget get you have still to add the damage from your E yet so your damage should be about 370 damage

I hope you liked my first guide, I will add Images later, if have something in your mind which would improve my guide, Comment.
PS I did this at 3am so there will be mistakes I will fix them when I get back up.