Keep in mind that this was this turn, where everyone got the chance to re-purpose a few resources. The Bone Tenders made up the difference by not spending much beyond deescalating the conflict and getting the Hunters calmed down.
If you want to guess how much culture you can safely spend, you will need to anticipate their actions next turn.
And no, you can't do a 0 Culture action. You will have to take some risks if you want to act.
Thanks for that information, though I still wonder how the Fishes was able to do the attempt at converting the Serfs. Also, how long are these crisis turns by the way compared to normal ones?
I will try to see if I can guess, the other factions next move.
The one faction that nobody was overly worried about was, oddly enough, the remaining hunters. In the chaos that followed the coming of the lowlanders, those who were most inclined to stir trouble had either died in altercations or left the valley to look for their beloved Great Deer. Nobody stopped them, since the few troublemakers were largely considered no big loss. The remaining hunters then retreated with their families to Rivercrossing, south of the Gentle River, and tried their best to stay out of the conflict within the valley proper. Chastised by Bone Tenders preaching, their appetite for bloodshed among the Valley People was snuffed out. And besides. They were too few left to do anything on their own. Willow and the remaining hunters did not return that year and neither in those that followed, making many believe that he and his had died on the lowlanders spears or beneath the snow of the mountains.
First, we can read about the Hunters and from as far as I can see, we should not expect them to true to do anything out of the ordinary.
If they get the choice between +1 culture or diplo action, I think they would simply take the culture and not use it. The exception being, that they might use the diplo action trying to track down what happened to the rest of the hunters.
We can probably also expect the Serfs to stay neutral and they might also simply chose +1 culture, which they give in surplus.
In the past years, the Artisans had focused their efforts to build a mine in the mountains to make Moonstone, haggling the price the Valley People paid for Azurite down to have the tools and people free to see it done. Word was that they were struggling to find workers for the mine though, as they held not much sway among the serfs that weren't already chopping lumber, hewing stone or otherwise making things for them. And then there was the food. Pulling people from the orchards to gather shiny stones while the larders were empty was bound to be unpopular. On the other side though, the Artisans had acted on their desires to grow ties with the lowlands fast. An envoy had been sent to Brushcrest, though what he was meant to negotiate, even the Bone Tenders didn't know.
Well, the big hint is that the artisans will try to find a worker for their new mine, so they will probably try to either influence the serfs to change jobs or convert a serf pop and then get them to switch job. This will then at least use 1 culture.
They will most likely use another diplo action on the lowlanders, but I am unsure what deals they are making and how that changes our income.
Most likely the Artisans will have a surplus of culture of either 1 or 0.
Meanwhile the Fishes worked within the valley to spread their own influence, though swaying only few of the still unaligned serfs. For them, the most important things was to keep the people well fed. If they managed that, so their plan, they could make the people see that the Hunters and the Artisans were wrong to lust after Moonstone, lowlander dyes and all these other things. After all, a nicely painted house didn't stop your belly from growling. At the same time, they were sending envoys to the White Clans, talking with the chieftains of a few clans that had many hunters and who had no stake in the villages being build in the mountains. Most agreed that they were planning to settle Clansmen in the valley to replace the many hunters who Willow had led to their doom, but a few were worried that the Fishes were trying to gather loyal spears under themselves for other purposes.
Well, it seems likely that the Fishes will try again to get influence amongst the Serfs and use a diplo action to finish whatever deal they are making with the White Clans, since we have not seen the end of that. Since they would have to either chose +1 culture or a diplo action, then I am unsure of how they can do both, but in the end, it will be unlikely that they will have any surplus.
Overall, I think that we at most can expect 3 culture in surplus from the other factions, though it might very well be lower than that.
Edit:
I forgot to think about that Silver is a Luxury good, that will provide 1 culture, so if the Artisans succeed in getting a worker, then they will probably get 1 culture back again.
Second edit:
Also, since the mine seems to be finished, the Artisans will have left over production, which they might attempt to trade away for Luxury goods. I am unsure what else they would do with it.