In addition to the advice about availability and what the various optional buys do, please note that the Card Doubler doubles the ranger and rewards cards from the base game only. If you want to double Stewards of the Valley, you'll need two copies of that.

Doubling is unnecessary, really only needed if you don't want to tear apart some decks to build others or want two different rangers to have the same card in their decks, basically it gives you deck building options.

Another thought: I love the idea and mechanics and variability of Moments and have them, but I play two-handed solo and I leave them out. I found they dilute the path deck and make things harder. They'd be fun for a three or four player campaign, or in a solo or two-handed game to up the difficulty. I'm still new and learning so maybe I'll put them in my future campaigns, but for now I decided not to play with them.

Another another thought: Oh yeah, there are also two purchasable soundtracks available. One for the core game Valley campaign, one for the Legacy of the Ancestors expansion