My opinion is that it depends on how long you have been in the relationship. For instance a ring on Christmas after only being together only a few months is not appropriate and might send the wrong message too soon. A watch or jewelry would be better.
Find a great gift idea that gives a memorable experience and relaxation, and a spa gift vouchers will be the best gift I am referring. Aside from a day of pampering and refreshment, they will also give a fun deals like a luxury accommodation and a best spa and massage services at choice.