Depends on where you live but Gardenias are a bit tempermental especially if you want to keep it as a houseplant. Gardenias are tropical meaning that their roots cannot freeze or the plant will die. The soil should be kept moist but not wet and after a month, you should give it a weak solution of a high phosphorous fettilizer once a week. Make sure the soil is moist before you fertilize to avoid burning the roots.
I am a retired horticulturist that specialized in tropical houseplants for over 36 years.