The thing about the "desktop humidifier" is that it won't humidify a space bigger than ... a desktop. And if that space isn't acutally enclosed to trap the vapor, even that is totally ineffective because the vapor diffuses so quickly away from the spot where the humidifier actually is.
So if you have an enclosure or can build one, this looks like it would be good for about a half to a whole square meter of plant space.
Do you have a humidity meter? Here's a pretty cheap and effective one, to help you measure results:
Thermometer and Hygrometer Gauge - Plant It Earth
$10 USD, which should be practically free in your currency these days XD