Gardenias like partial sun or filtered sun so if grown indoors half a day of morning sun would be ideal. Use a good potting soil that drains well such as Miracle Grow potting soil. As for  as pH or soil acidity gardenias like a soil slightly acid at about a 6 (with 7 neutral) so most potting soils will be fine. The big challenge is controlling white fly and low humidity. Mist often and wash the foliage to keep white fly from overtaking the gardenia plant. Keep growing, Marianne Binetti