Q.Gardenia Bush
I have a gardenia bush that I rooted from one in my mothers garden. It is very special to me. It is in a big flower pot. It is about 3 years old and about 18″ tall. I kept it in my sun porch during the winter. In early spring the leaves looked stressed, became wilted and turned brown. It looked completely dead. I kept watering it slightly and then put it outside in my garden. I was so surprised to see some life come back in little green leaves!!
Then last week I found the bud of a bloom!! My question is should I plant it in the ground or leave it in the pot? I am afraid to leave it in the pot and afraid to plant it in the ground!! Can it take full sun or does it need some shade? Any help would be appreciated.

I would keep it in the pot at this time. It's happy if its going to bloom for you! Gardenia are a very finicky plant, so the less stress the better.
Here are some articles that will help you with care requirements.
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/growing-gardenias-indoors.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/transplanting-gardenia-plants-planting-gardenia-somewhere-new.htm