While I'm horrified to admit this, I'm actually kind of good at this fashion junk now. The reality is that you need something on you neck, regardless of the "gilding the lily" rule. With your red hair and the copper of the dress and your lovely alabaster complexion, I am sure you'll be quite the lovely and striking sight. They key is to play up this lovely stark contrast and not overwhelm it. A carefully chosen pendant (not too large) on a delicate gold chain hanging equidistant between the bottom of your neck and your dress neckline should be just enough to say “notice my lovely shin and delicate collar bones” without fighting with the dress. Costume jewelry should allow you to find something copper / burnt orange to keep you from adding too many new colors. I know I bought something like this at Bijoux Terner at Logan for very cheap. The sets that come with matching mild drop earrings should do you :)