I want to learn Earth Spirit

I have 600 Hours on Dota (I do not play Ranked) and absolutely love this Game but I'm getting bored of my current Hero Pool and I'm looking for a Challange.

I really like Earth Spirit's Design both Visually and in Gameplay so I'm looking to learn this Hero. Here's my Questions:

• What are his best Positions, is he just a Pos 4?
• What are other viable Positions, van he be a Core?
• What are some important Items to build on him, can he build Damage?
• What are his most important Spells/Combos to learn?
• How do you make good use of his Ultimate?

Thank you in Advance and good Luck in your Games!