Gardenia plants are considered "prima donnas" by many when it comes to growing them as many of them are prone to root diseases.
I found the following two easy to care for. During the summer months they're outside where they get morning sun until about 1pm. During the colder months of the year they're placed under fluorescent plant lights and watered only when dry.
1 tbsp of bone meal and slow release Osmocote, 19-6-12, has been added to the soil. Once a month these gardenia plants get some Epsom Salt which is dissolved in hot water, cooled off and added to a watering can.
Gardenia coronata
Gardenia 'Diamond's Fragrant Delight'