Co-worker gifts for Christmas?

I received a gift from a co-worker this week and thought it was a sweet gesture since I'm new (a few months) I didn't expect anything / didn't plan to buy anything for anybody. I am feeling a little overwhelmed (maybe a bit obligated too) to buy a gift in return. It seems like the right thing to do and a nice thank you. I am not sure what to get though. I don't want it to be expensive / or too cheap. What is a good gift to give?