Seriously, Ornn looks like a champion who will either be useless or broken, no middle ground...
The whole concept of this character looks like it will end up like this.
Either he is in a viable state, in which case he is going to go totaly insane and be a must pick or ban, or he is nerfed to a point where noone will ever want him on the team.
The reasons for this are in the way his abilities work.
First, buying Items with no downtime is pretty broken. Ok, we dont know if he can buy everything, but just imagine him being able to restock potions in lane, without going back. And that isnt even the part that makes me think this ability is just busted by design. Its the part where every ally can get an upgrade that the enemy team cant get. This passive basically says that your full build team will have MORE SLOT EFFICIENT ITEMS than the enemy team every game that goes lategame. To make this clear: Your team is able to power up beyond the level of the enemy team. Your team has access to extra stats not available for the enemy team. Your team has access to better Items than the enemy team! There is absolutely NO WAY to balance this. As long as this passive stays at any level that can be considered relevant, its always busted.
Then there is his ability to make the CC abilities of allies stronger. Again, let me make this clear: In a mirror match, with the only difference being this champion, your team is already stronger than the enemy team by the start of the game. No matter how small the extra amount of damage and CC duration is, it is still more than the same champion would have if Ornn was not on the team.
And these things are literally just EXTRAS to the champion. They are not full abilities, they are passives, bonuses. He still has a full 4 spell kit on top of it.
He makes allied champions stronger with no sacrifice at all.
The only way to stop this from being gamebreaking is to nerf the champion to a point where he becomes a trollpick. As long as he remains viable as a champion by himself, he will be busted in a team wide perspective.
Honestly, who designed this champion and who decided that this was a good idea?
's worth of stats for 350. You are literally as strong as you would be if you bought a longsword. So it will only matter when everyone is full-build.
How did you describe it?

strategy, id buy 2x
and use 
or