The STEAM GUN receives general acclaim! They didn't realize she'd have the first one ready the same day.

How much ammunition and steam can it hold? How quickly can it be reloaded? How heavy is it? Will it sometimes explode if used too long? (This question comes from a previously quiet man in the corner.) Is the backpack too hot to carry when it's steaming? How far away can it shooot? Can they drop a magic permanent fire in the water and have it always steaming? Should they put some holy water in?

One woman has a flaming dagger (it goes whoosh! on command) and wants Waltana to make a sort of slot for it to go into so it heats the water but can be taken out in one smooth movement if she wants to stab something, she'll bid more if Waltana makes one like that.

They definitely want a huge one! ...but can't really agree who should have it. (They are kind of assuming she can only make One Huge Gun, instead of many small ones.) They could all bid for it but they also have some experience gambling and can tell a fool's game. How about they not raise the price, here, and try to work something out later.

This is a noble attempt and it works for almost a minute but it only takes one fool, doesn't it. "A hundred gold!", someone shouts, and the game is on. The wiser ones quit early.

Desnan travelers know all about learning languages!

Like any other skill, you learn a language faster the more you practice, and also the higher the stakes. If she were an adventurer she'd look for ways to bet her life on her ability to communicate, like following orders in a fight with demons, propositioning people, or filing tax reports. Buuuut ordinary people can learn languages too (Otho remembers doing it before he was an adventurer!) and so there are some mundane techniques for her to practice.

Since she doesn't have a dictionary, she should write down a lot of word pairs while she has the spell, and some her-native-language descriptions of Taldane grammar. And then she should start spending time with the spell off, mingling with natives and listening to them and trying to talk to patient people who are willing to indulge her early efforts. She should run errands, like shopping, even if she can barely get them right. 

"Your biggest problem is that my spell lasts twenty-four hours. I could delay casting it next time, but then you'd have to find me if you had suddenly had to talk to someone. Ideally you'd have an item you could put on and take off, but there probably isn't one for sale here in Kenabres..."

Meanwhile, the spontaneous auction winds down, with a proud and possibly lucky winner who is going to offer her a thousand gold for the REALLY BIG STEAM GUN CANNON MAN-PORTABLE SIEGE ENGINE.

...their idea of what the BIG GUN will be like might have grown a bit in the telling. What, uh, exactly will it be capable of doing? And will it really be as man-portable as in their wildest dreams? 

(Things that are known to exist: ballistas! They are essentially huge crossbows, and can be made to almost any side and correspondingly power, but only a giant could lift and aim one. They're usually placed on fortification walls.)

She blinks owlishly at the demon fighting and propositioning bit of the advice, and decides to ignore it. Thanks Otho and writes down the idea of word pairs and immersion, planning to start on it later.

Talking about MECHANICS is much more compelling. A thousand gold will buy her enough steel and weird alchemical supplies that she'll customize it! Building big and powerful is easier than building small and powerful- Getting anything seriously capable out of a crossbow-size device would mean higher quality materials, more finicky construction, less easily repairable by someone who is not her. She was thinking- She starts sketching, a boiler and a large tube with a frontal shield built into a wagon- For a thousand gold she can make it self propelled and use a large tube to fire heavy shot, which can be explosive or just solid. This would almost mean you need two or three people, but even given how unnaturally tough the vrocks she fought were a 7.5cm shell exploding in one would turn it into chunks and probably damage its friends too. Though making the really good explosives is also expensive. Or, instead of firing large, heavy shot focus on rapid fire of smaller ones, like her wood pile-chunking demonstration, something quite similar to that that ends up weighing about a hundred pounds in total would be very doable. Or, skip the mobile wagon and focus more on making it man-mobile, something wheeled that a single strong person can haul around and drop prone to aim and fire, if not carry over the shoulder, maybe 3cm? Or go all the way towards man-portable and use the best materials she can get her hands on and probably lightning-tech to make something a single strong adventurer can carry and fire?

There's a lot of options and tradeoffs even for something so simple as using steam to fling bits of metal!!! She'll tune the result towards whatever he wants, or if he doesn't want to get into the nitty gritty, pick a size (smaller is less capable and harder for regular craftsmen to maintain) and a damage profile (high impact, rapid fire, or somewhere in the middle), and she'll figure it out! And she'll include a bunch of spares and also lessons, at this price!!