You can do the following simple steps to use the Twitter client gem:
# get user id from user name
id = client.user( 'user_name' ).id
# read user's timeline by id
timeline = client.user_timeline id
# read user's timeline of yours
your_timeline = client.user_timeline
you can omit the username, and you get the timeline of current user, so try also to issue:
user_info = client.user