Work In Progress
Let's start off by saying all I know is Pubs, and All Pick at that, because Earth isn't available for pick in other modes. That being said, at the time of writing this guild I have 90 games played with him with a 65% win rate and a 3.5 K:D ratio, not to mention at least 300 teammates saved from certain death and well over 2000 assists since I get around 20-30 assists per game.
So you have seen my item build above, Let's talk about items I consider situational that many others have been making Core to their builds.
I have tried Force Staff many times and almost always find it to be unnecessary. I do consider it a Luxury Item though and is a good way to get yourself out trouble if you make a bad decision which we all do once in a while. For saving teammates, use your abilities you already have. If that's not enough...then you probably arent winning this game anyways because people are not playing smart.
Arcane Boots...The mana gained is not enough to even do a full combo. Any 150% mana regen item + a bottle is better for your mana problems. Maybe if you are the only support I can understand it but I don't like him as that kind of support.
I have tried many different item builds, but I have one key item that I have discovered is the key for my style of play. Eul's Scepter. 150% mana regen, +10 int, +40 movement speed. I personally opt for a Tranquil Boots so the speed gained from the Eul's and boots combined give you far more overall mobility.
This build is all about getting your speed, mana regen and armor up quickly with items that have actives that are helpful to your team. This guide works great as a mid or lane, support or carry. It has been working great for me and the Eul's Sceptor has been the key. The speed and 150% mana regen it gives you is paramount and the active helps you to escape when you need to remove an enemy, teammate or yourself from battle for a quick get away or set up. Medalion of Courage gives you 50% mana as well as 6 armor that you can then activate on an enemy removing the 6 armor from both of you. After you have these two items you will have no more mana problems. The tranquil boots give you the bonus move speed and health regen while still allowing you to be a caster. You can place, pull, and kick rock, without the boots being broken. Veil gives you armor and stats and increases the damage of your ulti as well as team spells.
You are not a tank. That is not your roll. Your job is to stun, roll in, ulti, veil active, kick enemy back to your team and drop rocks on everyone effected by your ulti. with your speed and armor items you should be able to roll in and do all of this and then escape because no one smart is gonna sit around in your ulti trying to kill you. But remember, you are not the tank. You are a caster and you do low damage by right click.
Save your rocks. Once you have sufficient mana, remember to kick and pull them around the map with you, because your ulti is amazing with 5 or 6 rocks to drop down near effected enemies.
Remember to push and pull teammates to saftey. Kick enemies into other enemies. Kick your teammate Ursa into the enemy after you stun. SO many things you can do. Be creative. You Rock.