[ ] The Promised Wand [5 Gnosis] - A simple wand, nice and supple; eleven inches long, made of holly wood, and possessed of a phoenix feather core. An uncomplicated grip made from uncarved wood in the style of an ordinary tree. However, this wand seems to possess an extraordinary affinity for you...
First thing's first, let's think a bit on the reason why this choice costs five Gnosis. It is entirely possible to make this wand in the Design Your Own section, without spending a single shred of Gnosis, even, so presumably it is not any of the components, whether alone or in concert, that have caused the price tag. The next thought is that it could be the possibility of Priori Incantatem, like other posters have described. Being able to greatly tilt the odds in our favor the first time we fight a
You-Know-Who with access to His wand is certainly a boon we'd probably be willing to pay more than 5 Gnosis for, in the moment, so picking it up now would be a bargain.
However, I don't think that's it. Or at least, not entirely it. Note that last bit there: "this wand seems to possess an extraordinary affinity for you". It's important to remember that wands are, in a general sense, alive. They display an awareness of their surroundings (switching allegiance based on the results of duels) and both form and act on opinions (wands liking/not liking different personality traits in wielders and/or styles of magic). Someone's personal wand will perform better for them than a wand they get from someone else in pretty much all cases. In my view, it's better to think of wands as closer to the likes of Pokemon or Digimon than as simple tools. Having a good relationship with the one you have is just as if not more important than having a 'good' or 'powerful' one, as that bond you share can motivate it to go above and beyond what it's supposed to be capable of.
So my thought as to why this option costs Gnosis is that bit about the wand having a really good affinity for us: it likes us and genuinely wants to work with us, making the task of spellcasting much easier than if the wand was merely indifferent.
That's my thought on it, anyway.
I broadly support saving Gnosis for big purchases, given that big purchases should be the more cost-effective option as compared to many little purchases. That said, the chance to pick our first wand only comes once, so I'm willing to splurge here. I'm undecided on whether that means The Promised Wand, Affanc Hair, or Ancient Roman Wand Wood, however.
But now, time for some fun with and/or thoughts about the wand design section:
Dragon Heartstring + Even Longer + [Insert Flexibility Here] + Ancient Roman Wand Wood = UNLIMITED POWER!
The Flexibility doesn't really matter, but the other three options make this what-the-fuck tier powerful. On the upside, this thing'll probably let us rearrange landscapes with ease. On the downside, said rearrangement will probably be done solely through explosions, at least at first. But that amount of power, properly harnessed? Goodness gracious would that be amazing. And if anyone is going to be able to harness this monstrosity, it'd be a thrice-great, at least in an area of their expertise. Probably not gonna go for this, but the explosion memes are tempting, not gonna lie.
Phoenix Feather + Short/Average + Supple + Holly = Cheapskate's Promise
So yeah, the discount canon build I mentioned earlier that costs zero points. Presumably we lose out on some benefits getting it this way without spending the Gnosis, but it's possible to make.
Affanc Hair + [Length] + [Flexibility] + Holly = I Spent An Afternoon Studying It
I see that it's been mentioned by others, but I feel it bears repeating that Holly's property of boosting core properties presumably comboes quite well with a core that has enough benefits it costs 5 Gnosis. Presumably means that we can pick up new magic much quicker, although I'll note that because it specifies "picking up new magics" presumably the core boost doesn't help when training existing capabilities.