If you want to have the api and impl jars included for you by GateIn, you don't need to set the web.xml context-param to anything, as the default behavior is to add them to a portlet deployment.
As for adding the Richfaces extension, you just need to add that single jar into the WAR. Obviously its a good idea to ensure its the same version as GateIn will add otherwise there could be conflicts.
Thank you Ken. That makes sense.