In my school, we typically organized presents as an entire class, which allowed us to buy something more extravagant (like gifts typically in the $200 range) and made the whole process less awkward for those who don’t normally buy gifts for teachers or don’t know what to buy.
It depends on the teacher. Make the gift personal, thoughtful and witty (unless they have absolutely no sense of humour) with a poignant card. Here are a couple of things we did:
An old English teacher of mine: his year 12 class bought him a watch (so he can keep track of time, because he ALWAYS gets carried away during the lesson and holds the class back during recess and lunch), an illuminati board game (he is obsessed with his conspiracy theories regarding illuminati and MH17) as well as a German national football team shirt (apparently he hates the Germans lol) and a book. They are also planning to give it to him next year to reflect the amount of time he takes to mark essays (he takes a term and a half to mark an assessment, and still hasn't given me back my year 10 and 11 essays…).
A couple of other teachers: t-shirts with witty line or quotes such as ‘but first let me take a selfie and send it to my friends in Italy…’, ‘The mask (his name has the same syllable) cell triggers a raw 50 in Bio response (in hindsight, seems appropriate given the number of people who got 50 in Bio last year

) ’, ‘grammar, grandma, grandma’ (one of the English teacher’s pet peeves, he is obsessed with the power of grammar).
My English teacher this year: My class didn't really know what she would like as she doesn't really have much of a personality to be honest, so we brought her a bunch of face/hand creams and scented stuff from a really expensive French shop (she ended up liking it surprisingly).
My Maths teacher: didn't want anything material and wanted us to instead to contribute $5 each to UNICEF under his name.
Other stuff: macaroons, concert tickets, personalised mugs, recipe books, Macbook and holiday (like legit)