There is no letter equivalent for Gar
There is no rune poem for Gar. It is a Northumbrian Rune.
The Spear rune, a symbol of Yggdrasil, and the Pole Star, the cosmic center and axis, is the rune for this week. There is nothing but potential and possibility that can be had, and actions and events are free from Wyrd and Orlog, in the sense that they will either be ending a chain of events, or creating new ones. How they turn out are yet to be seen, and perhaps are not being shown as that information is not available or needed.