HI Miss Christine!
What an exciting choice for you

merry Christmas (happy holidays)

There is a section on the tiffany website which has a section of items $500 or under. It might be fun to take a look?
What about the ball ring? It says its $200 on the tiffany website. It might go with your ball bracelet nicely? The matching drop earrings are $285 (you could get both for $485 haha

). It might be too matchy, and it may not be in your personal style either.
For the question " what would you pick" - looking at the <$500 list - there are so many amazing things in there that I could buy (and have bought) myself haha.
Personally, id probably get something quite different from what I had already, as to match with different outfits. Like the Tiffany T smile bracelet for $250. One of the lacquer bangles for $465. Or something from the graffiti collection in gold or rose gold $465-$500.
Of course it depends upon your style and what coloured metals you like (Ag/RG/Yg).
Wishing you the best of luck! Such a fun choice