non-consecutive pass?

I think you are referring to the Seishun 18 ticket. You don't need to buy this online, it can be purchased from the JR counter in Japan, but only at certain times of the year, so you'll want to watch out. There's more information on it here:

http://wikitravel.org/en/Seishun_18_Ticket

Also, you can't ride the Bullet Train travel with a Seishun 18 ticket, only with a Japan Rail Pass, so it kinda depends on how long you have in Japan and how far you want to travel.