What's the fastest way (fewest actions) to earn the most valuable commodities?
The fastest way I've found so far is in Mahogany Hall; it requires a very high Persuasive skill. If you train the Louche Devil and teach him Philosophy, you'll get 111 Nevercold Brass Slivers per action and increase your Pygmalion quality. When Pygmalion reaches 17 or 18, you should be safe to take him out to a Society dinner, which gives you 1000 bonus slivers. ... You can then re-train him as often as you like to rack up lots of Echoes.
If you want to do it with your Dangerous, head to the third coil of the Labyrinth of Tigers. "Avoid becoming an exhibit yourself" and "Fight back" for ~1 Echo per action. (Most of the actions in the third coil earn ~1 Echo per action, but they require a very high Persuasive as well.)
This is a difficult one to answer; given the link between Stories and Qualities, it will be different dependant on what is available to you.
As a general rule, completing a series of linked Stories will carry greater reward, but this can become inefficient if the Story is difficult for the determining Quality (failed attempts receive no monetary reward).
As for a specific tip; I would recommend searching the ruins in the forgotten quarter in the early game. The reward for the lowest level option is based solely on luck, and the cost of entry can be reasonably quickly reclaimed. 10 x relics @ 5p with a 50% success rate = 25p/adv.
It appears that you gain more valuable goods for completing more challenging stories. I would suggest focusing on a single statistic to unlock more rewarding stories. Risky and Chancy challenges seem to increases stats very quickly. When you want more loot per action, seek out easier stories.
Keeping on hand Second Chance items earned through social activities (Chess, etc) improves your chances of success in stories and is worth spending a few actions on.
I think most storylets are pretty well balanced. Labyrinth of Tigers and Mahogany Hall can give you about an Echo per success, but you also need stats of 90-100 to play.
So if all you're after is money, concentrate on one stat, because the rewards seem to be tied to that.
Also, many of the longer-term sequences (e.g. ones with Running Battle) can have big payoffs at the end.
Once your stats are at a reasonable height, most grinding yields about an echo per action, but that's at straight bazaar prices where it doesn't matter if you're talking rostygold or glim or rats or whatever - but if you go with a grind that yields an improvable currency (foxfire candle stubs, glim, jade fragments, souls, stolen correspondence, lamplighter beeswax, whispered secrets, prisoner's honey, silk scraps, proscribed material, primordial shrieks, greyfields 1882) then grinding it high enough to bulk trade up through the chains to completion, and then selling finished products - Way more lucrative.
Once you become a Person of Some Interest then you can do "Unfinished business" storylets at the main quality based locations like: Spite, Ladybones, Veilgarden, Watchmaker. The options that require 5 or 6 actions give random results but on average they give 1.5 Echoes. It's also less time consuming if you just need 2 clicks for 5 or 6 actions rather than 12 clicks for 6x 1 action.
I've found that bulk converting upwards is actually action inefficient and unprofitable if you work out the rewards. It's not "lucrative" at all.
The devs don't like people talking about Fatelocked content, for good reason, but if you choose to become a Spirifer, you gain access to a storylet that will provide you with roughly 1.74 echoes per action /on average/, if you use the Unfinished Business storylet in Spite to grind the requisite resource. Sometimes you'll get less than that and sometimes you'll get more than that; Unifinished Business storylets are unpredictable.
Keep in mind that this post assumes you're at the stat cap. The higher your stats are, the better your average will be.
If you haven't spent the Fate, or chose the other option, you can do the Affair of the Box Carousel; that's slightly less profitable at 1.6 Echoes Per Turn, but, y'know, it doesn't cost real money.
EDIT: If you're somehow looking at this and not at the official wiki's money-making guide page, every suggestion here is horrifically outdated. Even in the midgame there are now options that provide well over 4 echoes per action, and in the endgame you can hit 6EPA. Look here for more info.
The Writer's Desk storylet is accessible from persuasion 10 in Veilgarden pays off very well, although the action cost per "cycle" is relatively great.
Anyway, according to some math I did, always publish as competent, write rapidly from 54 persuasion onwards, and frienzedly from 189 on, and the payoff per action is:
- 0.24 - 0.37, for persuasion 10-17
- 0.37, for persuasion 17-53
- 0.37 - 0.44, for persuasion 54-67
- 0.44, for persuasion 67-188
- 0.45 - 0.55, for persuasion 189-249
- 0.55, for persuasion 249+
Of course, long before you get that far, much better sources of income will become available.