Welcome to Nikonians! If you are looking for both a portrait lens and a macro lens, I would recommend the Nikkor 60mm f/2.8G ED AF-S Micro though it is about $50.00 over your $500.00 budget.
Since you already purchased the 50mm f/1.8G AF-S you could add the Nikkor 40mm f/2.8G AF-S DX Micro ($276.95) and be just under your $500.00 budget. Good Luck and Enjoy your Nikons!
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