So, I've just double-checked the WtF book and I think I've been misunderstanding how buying Gifts is meant to work in terms of Experience for the last few years. That said, I'm not really sure how to parse this section, and the process more broadly. Would someone be able to explain this succinctly?
So in order to buy a Facet of a Gift, you first need to "unlock" the Gift. This costs 3xp for Gifts you have an affinity for (from either auspice or tribe) and 5xp otherwise. Unlocking a Gift gives you your first Facet in that Gift. Afterwards, subsequent Facets of that same Gift only cost 2xp a piece. Additionally, whenever you get another dot of Renown, you can learn a new Facet of a Gift you've already unlocked for free, so long as the Facet you're learning is of that Renown.
Note that this whole thing only applies to Shadow Gifts. Wolf Gifts always count as unlocked and the Facets only cost 1xp, while Moon Gifts are... a little weird. The Moon Gift matching your Auspice you get for free, and you automatically learn the next Facet in that Gift for free when you gain a dot of your Auspice Renown. Moon Gifts outside your Auspice cost you 5xp to unlock (which gets you the first Facet), and you can be the subsequent Facets for 2xp.
So as an example, let's say I'm playing an Irraka Boneshadow. I have 1 dot in my Auspice Renown (Cunning), so I have the first Facet of the New Moon Gift. I decide I like the Gift of the Elements, so I buy the Wisdom Facet of that Gift. Since this is the first Facet I'm buying of the Gift of the Elements, I have to pay the xp surcharge to unlock it. Since I'm a Boneshadow, I have an affinity for this Gift and so I only pay 3xp total to learn the Facet and become a waterbender. I like this new Gift so much that I eventually decide to buy the Purity Facet and become a firebender too. Since I've already unlocked the Gift, the Purity Facet only costs 2xp.
Later, I earn a dot of Cunning Renown. This lets me learn a Cunning Facet of an already unlocked Gift for free, and since I'm so close to being the Avatar already I decide to use that to learn the Cunning Facet of the Gift of the Elements. I also learn the second Facet of the Gift of the New Moon for free, since Cunning is my Auspice Renown.
Finally, I decide to learn the Wisdom Facet of the Gift of the Pack on a whim. Even though this is the first Facet of that Gift that I'm learning, it still only costs 1xp since it's a Wolf Gift.
Does all of this make sense?