Q.can a gardenia do well in NJ?
I have a very large plant and I want to know if I should put it outside for summer and bring inside for winter.

Gardenias will grow outdoors in USDA plant hardiness zones 8-10. Most of New Jersey is in zone 6, so your gardenia will not survive outdoors year-round. You can put it outside for the summer but you must bring it inside for the winter. I wouldn't bring it outside until temperatures consistently stay above 50F.
For more information on the care of gardenias, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm