What nobody tells you is that skincare devices can be a double-edged sword. Yeah, there are useful things like a good ultrasonic cleanser or an LED lamp, but a lot of girls end up with a drawer full of gadgets that promise the world and then don't fit with what they're already doing. The biggest risk is that if she already has an established routine and you throw a device at her that requires changing it or takes time to learn, she probably won't use it as much as you'd hope.
Instead of betting everything on a gadget, think about something hybrid: a treatment or product from a brand she already loves or wants to try (those premium brands she's dying to get but won't buy for herself), combined with something smaller and more specific. For example, if she's obsessed with skincare, she definitely knows exactly what's missing from her routine. A casual question to her friends or a peek in her bathroom tells you more than any bestseller list. And if you really want to go for a device, pick one that's genuinely easy to use with no learning curve, like a jade roller or rose quartz roller (I know they seem old-school, but they work).
The best strategy is to indirectly ask her what she's missing or what brands have her hooked lately. Then surprise her with that - she'll definitely thank you more for it than for something random you guessed at.