I got a little nervous to answer about the complicated fare rules while I like to check AIR fares.

But I remember, JR has a nice special ticket for foreigners.
http://www.jreast.co.jp/e/suica-nex/
With this you don't have to be bothered about the rules.
The 1500yen portion covers and takes you to Ebisu via Shibuya.
The 2000yen portion is Suica. It is a pre-paid fare storage card, which you
can use for buying something.
This is a steal.