Gandalf (Ian McKellen)’s Timeline and Summary

Gandalf's story precedes the others, taking place during some of the events of The Fellowship of the Ring.
As the Balrog takes him into the depths of Moria, he grabs his sword and fights it as they fall.
After much combat, Gandalf defeats it, and then enters some sort of ethereal state which seems to last many ages.
Finally, he wakes up, and barely remembers who he is.
With his new white cloak and white staff he heads to Fangorn where he meets Merry and Pippin and, presumably, tells them to chill with Treebeard.
Then he hits up Aragorn, Gimli, and Legolas, with whom he stays.
The four travel to Rohan where Gandalf breaks Saruman's hold on King Théoden.
He tries to council Théoden to stand and fight, but Théoden refuses, instead opting to retreat into Helm's Deep.
Gandalf leaves the people of Edoras and searches out Éomer and his company of horsemen.
He tells them of their people's war and brings them to the battle at dawn where they route the orc army.