after you send initial presence, you will get a roster.
http://xmpp.org/rfcs/rfc6121.html#roster-login - how to retrieve roster after login.
to get somebody's presence, you need to send a presence IQ. then get the status element.
if you want to have a look at my xmppp client that i've built using strophe.js, please go to: http://hularing.me/