New players, or returning players who did not log into the game at all between November 2019 and mid-March 2020 were given the option of a free deck. It’s possible you didn’t qualify if you logged at all during that time period (even if you didn’t play a single game). Alternatively, if you chose to skip the “New Player Experience” when you came back, you might have lost the opportunity to get that free deck (along with all the extra freebies you get from climbing through the new player ranks).
You can find more information about the free decks here, and the decklists here.
Galakrond’s Awakening is 2800 gold. Yes, the first 700g only gives you half a chapter, but chapters 2, 3, and 4 unlock both sides of the story for 700g.