Jewelery is a sure fire way to get the underpants around the ankles so start thinking about whether you think a necklace or earrings are the her thing, also pay attention to her current jewellery - does she like gold or silver? My last girlfriend had a thing for white gold so that was easy to choose. $200 should easily get a real nice necklace, you can scrimp on the chain because she may not know the difference between a silver chain and a not-so-silver chain however the neck piece is where your plastic starts to melt in the EFTPOS machine.
Kuma, You've gotta get out from behind that secretary desk of yours more often mate.