As a former professor (USA) (now a full time research scientist) let me add to the chorus: NO GIFTS, EVER.
Gifts to a superior are a propitiation; I would not only refuse gifts from a student but report the attempt to my department chair, so I wouldn't be compromised by not reporting an offer of a bribe in the future. I would probably have to rescind my offer to advise you, and let you find somebody else.
Your urge to give a gift is called propitiation and it should be quashed; it IS a bribe to gain favor, not thanks. If I selected you, it was not to do you a favor, but because I thought with my management you could make a contribution to our field. If I didn't think that, I would spend my time on someone else, or on my own research.
Saying thanks is enough. Don't offer to buy me lunch, don't offer me tickets to something, don't try to use money or anything else of value to establish a personal relationship with me. It is possible we WILL become friends by the time you are ready to defend. I became (and remained) friends with my advisor. If that is going to happen it will be a result of shared cultural interests without any gifts being exchanged.