Directly arm the Iraqi Kurds.
The Kurds are clearly the most effective ground fighting force opposing the ISIS death cult. Bypass the dysfunctional Iraqi central government, which seems determined to limit the effectiveness of the Peshmerga by slowing delivery of supplies and under-equipping them in an awesome display of paranoid short-sightedness.
The central government must understand that the wolves (ISIS) are at the door, and starving their most effective forces of essential supplies is suicidally stupid.
First matters first - defeat the unparalleled evil, cruelty and inhumanity of ISIS - then work to establish a more inclusive, representative government. That seems to be the greatest hope for sustaining Iraq as a single national entity.