All you need is one friend willing to start up with you, you don't need to start a guild or anything.

Regardless, the social aspect wasn't your question. I would recommend picking up two things to start; a starter deck like Mat already said, and an Epic Collection set.

The Epic collection set will give you SIX packs of cards (which is about the cost of the box collection itself), a card box (with dividers), a deck box (with sideboard divider), a playmat (I use mine as a giant mousepad, who the hell whips out a giant may whenever they play? lol), a couple extra cards (foil heroes and a guaranteed loot card), and a checklist for the set in full colour, illustrated book form (quitelike the M:tG set lists if you've seen those). The Epic Collection box can be found for a number of different sets and is a great solution to organization as well as jumping into new sets.

I think you could pick up the Epic Collection AND the starter deck together for under fifty dollars (orabout $55-$60 if you're in Canada).

I hope you see this, despite it being buried in the godawful comments section this place has, Mat should have mentioned the Epic Collection to anybody interested in starting the game.