Episode 1.1 is "Stung!" which first appeared in DFC #30 (the 2008 Christmas issue). Jack is about to face a duel to the death when he finds an ancient two-headed coin that's destined to change his life forever. Get "Stung!" from the Kindle Store US here and UK here.
Episode 1.2 is "The Door in the Water". Jack meets Gus for the first time - but it's in a dream, so maybe it doesn't count. And when he wakes up he goes witch-hunting, only it turns out the witch is the one with the killing jar. That's in the Kindle Store US here and UK here.
Episode 1.3, "The Wrong Side of Bedlam" sees Gus (that's Talisin of the Shining Brow to us) escaping from a padded cell, Jack trapped in a witch bottle, and the boffins of the Royal Mythological Society explaining what's in store now the green comet has reappeared. It's in the Kindle Store US here and UK here.
And if you don't have a Kindle, don't despair, because all of those early episodes are online right here.