FireBrick MAC Graphs

The FireBrick is able to graph traffic for each MAC or IP address it sees.

From the manual:

There is also an option for set-graph-source-mac which causes the session to set a (forward) 
graph that is based on the MAC address of the source packet, if from an Ethernet interface. 
The graph is created if it does not exist. If set-graph is also defined then each new session 
created also causes the speed settings and long term shaper parameters to be copied from the 
named graph (in set-graph) to the MAC named graph being used. This is aimed at management of 
open WiFi and the like allowing a named shaper to be defined and a copy of its settings created 
for each client based on MAC address.

Assuming you have no current outgoing ruleset, create one such as:

 <rule-set name="LAN Outgoing" source-interface="LAN" no-match-action="continue">
     <rule set-graph-dynamic="mac" action="continue"/>
  </rule-set>