the-witcher-3
When I get to a new town, I always check the merchants' merchandise, and often they have crafting diagrams for armor and weapons that I can't use yet because I'm too low level.
I'm wondering, should I buy them or hope that I loot better diagrams? Also, are those diagrams sold by merchants unique? I don't recall seeing one from the merchants' stock that I already had, even the low-level ones.
I'm lv9 and I've never even seen this 'Full Moon' potion. According to the IGN game guide, there isn't a 'Full Moon' potion.
The Wikia states that the Swallow potion recipe is given to you in the Prologue.
Geralt receives this potion from Vesemir in the Prologue during the Defending Kaer Morhen quest.
So you should already have the Swallow recipe available, but you'll need to craft it using the correct ingredients.
Here's what you need:
Drowner brain (1): This ingredient can be found by killing Drowners, which are blue humanoid sea monsters that are usually be found near water. Common locations in White Orchard include the southern shoreline near the ransacked village, the swamp lands to the south of the Nilfgaardian garrison, and along the shoreline to the left of the Ford signpost.
Dwarven Spirit (1): This alcohol can usually be found in Smuggler caches and treasure chests or bought from any White Orchard merchant for 47 coins.
Celandine (5): This herb is super common and can be easily found in the environment. An easy place to find them is outside the herbalist's cottage. They can also be bought from the herbalist for 5 coins each.
This is what Celandine looks like.
It might also be worth updating your game, as v1.04 patch has been released.
Edit: I've been informed this has been patched and can no longer be performed.
In short, the merchant at "Odrin and Friends - Bottlemen" in Novigrad. Here's the long of it:
Most merchants are very stingy when buying your loot. There are a few merchants though that buy at 100% of the item's value. So a stack of junk that may usually be worth only a few dozen crowns is now worth several hundred. But the catch is these merchants have limited funds and replenish those funds slowly.
However, there is one such merchant that you can pump up his crown supply at no cost to you and fairly quickly. His shop is "Odrin and Friends - Bottlemen." It is outdoors on the docks on the north side of the central Novigrad island. The closest fast travel sign is Hierarch Square, which is still a while away.
This merchant buys anything and everything (even monster trophies and foreign currency, but not quest items) at 100% of the item's value. He has 500 crowns to start. He also sells about 230 Empty Bottles at 1 crown each.
An Empty Bottle sells for 1 crown to any merchant willing to take it. So buy a bottle from the Odrin merchant, sell it to another merchant, and you break even. His Empty Bottle supply replenishes completely each time you exit his shop and reopen it. (I have found it stops replenishing when you have a few thousand bottles in your inventory. Getting rid of them causes his supply to return though.)
When he runs out of crowns after you sell your junk to him, buy his Empty Bottles, sell more stuff, exit his shop, reopen it, and repeat to the point where you have sold everything for 100% of its value.
At this point you should have hundreds or thousands of Empty Bottles in your inventory. Each worth 1 crown. It can be difficult to find a merchant to dump them all on in order to exchange them for cash. For this part, you can go to the Loan Shark near the Oxenfurt Gate fast travel sign. Dump them all on him.
When he runs out of crowns, buy his 500-1500 florens to add 1500-4500 crowns to his supply. His stock of florens also replenishes when you exit and reopen his shop, so you can use the same trick here as you did with the Odrin merchant.
Finally to get rid of the florens, go to the Vivaldi Bank by fast traveling to Hierarch Square and exchange them for crowns at the same rate as what you bought them for.
Best Answer
As a general rule, the best craft-able gear at any given level will be the green-quality Witcher gear. Witcher armor will have the best resistance to "monster" damage in the game by quite a bit. Also be aware that, for those few times you need it (cough Extreme Cosplay cough), Cat school body armor & boots and Griffin school gloves & pants give unmatched resistance to Elemental damage. So be diligent in purchasing "maps" that lead you on quests to acquire those plans.
One of the main exceptions to this rule is that some non-witcher armor can be found with slightly higher resistances to the slashing/piercing/bludgeoning damage you will receive when facing humanoids. The free armor provided by the master armorer after you activate her is an excellent example of this, and won't require a diagram from you. On my 1st play-through I wasted a fair amount of my carrying capacity lugging around a spare armor set just for fighting humanoids. You should find witcher gear more than up to the task.
You will also be acquiring many low quality rune stones as loot. As such, I purchase on an as-needed basis the diagrams that allow me to combine these lower quality rune stones into their higher quality counterparts because these are diagrams I expect to re-use.
Very late in the game you might outgrow your "master" level Witcher swords. By this time you are very likely to have already looted a level appropriate diagram or weapon. Otherwise, sure, go ahead & buy one...
You will quickly find the crafting interface crowded with useless extra & obsolete diagrams just due to your routine looting. You'll quickly wish they'd included a way to filter out "grey" level or non-Witcher diagrams. There is really no need to spend your cash to accelerate this problem.