I asked some folks at Comic Vine to lead you into the Deadpool franchise.
A friend of mine in the comic books discussion thread of AV asked which Deadpool comic books should he start on. Being a new person who haven't read comic books, it's hard to keep the thread alive.
I would say to start with the ongoing that began during the Skrull invasion. THIS ONE. I guess he could jump in wherever but he definitely needs to read the DEAD arc.
I'm not big into Deadpool, but Joe Kelly is considered the Deadpool writer. He basically created Deadpool after he was created.