I'm going to get my wife nothing for christmas
Why aren't you going to buy something for your wife?
I got my wife a diamond ring for her birthday, now I can't give her anything more since it would be awkward
You can get her a smaller gift this year instead. She would appreciate anything especially if you already got her a big gift already. Not getting anything at all would be rude.
I am also broke after spending so much on the ring.
If you cannot afford something it might be better to give her a small gift or an experience. Some places have ice skating in the park or other free activities you could make a fun little date with.