Set path 1 to overflow to the second group.
Then program a second path that only contains group 2.
Set path one to ring to path 2 if path 1 is unavailable.
Also be sure that in agent group 1, you do not select the option to queue to the group if all agents are logged out.
The timers control how many rings before overflowing to path 2 is in path 1.
Ralph