How can I buy this when it says only 1 per person, but I need to grow these to advance in levels.?
You have harvested it. It's listed as Pot of Gold in your list of fruits harvested.
You also need to harvest one of each colour of Carmena Aviflora, which you haven't yet done. You've harvested red, yellow and blue, so you need green. You can change the colour with sparkle dust if you need to, once you have another which is either fully grown or ready to harvest.