Gardenias, help needed.

[Marietw]

Thank you.

[ginger]

From The RHS encyclopaedia:

Genus of evergreen shrubs and trees, grown for their flowers and foliage. Frost tender, min 15C. Prefers partial shade and humus-rich soil, well-drained, neutral to acid soil. Water containerized specimens freely when in full growth, moderately at other times. After flowering, shorten strong shoots to maintain a shapely habit. Propogate by greenwood cuttings in spring or by semi-ripe cuttings in summer. Whitefly and mealy bug may cause problems.

[Marietw]

I have a gardenia in a pot of compost, but I seem to have been given conflicting advice as it doesn't seem to be doing so well.
Any advice on position, food/feeding, watering, sun/shade - in fact  any information would be gratefully received.
Thanks  in advance from a very new gardener.
Marie.