Hello everyone. I am a bronze 5 challenjour with over 10,000 dominion and aram games.
I have over 30 level 1 smurfs. Basically, I am more than qualified to inform you on the right way to play sion.

Because your build is full damage, attack speed will help.

You need as much damage as possible because that is what your builds is for

5 Infinity Edges - This is for 100% crit chance and 400 AD
Last Whisper - For the 35% armor penetration and 40 AD

Just max is like I do. It is too much to explain. To put it simply, you dont need your q because that takes too long to charge up and you will be wasting aa time.

Double tp is the meta right now. Its op.
You can gank bot lane and return top without missing a single creep. It also makes split pushing easy.

Why full crit sion top in a tank meta? Because sion has infinitely scaling tank.
Basically he is a natural tank. Combine that with tons of damage and hes op.

You should play this in ranked. Its practically freelo. Normals is a joke because you can play anything in normals including ap vayne jg.

Pros:
-Tons of Damage
-Tanky
-Can be played anywhere including ADC

Con:
-You might run into walls and stun yourself

Do not miss a single cs
You should have around 200-300 thousand cs by the 10 minute mark
How else will you super scale?

You dont need a team. Just solo them 1 v 5. If your team is annoying, just win 1 v 9.

One man army sion is op. Good luck and have fun with the freelo in solo q!