Need to buy jewellery for my wife

I don't have much experience in buying jewellery, so any help or advice will be appreciated. Looking to buy either a nosepin or a pendent for her gold chain. Budget is as low as possible but don't want artificial. Don't care for resale or 'true' diamonds, a moissanite or lab diamond will do as well.

Other stones that go with everything will do as well if you can let me know.

Looking for any local recommendations or even online ones.