Mike,
Bareroot it and put it in Als mix in March.
The soil can't be that bad, it's blooming when it is suppose to, many gardenias are blooming now.
Gardenias like to be pot bound by the way.
Be patient.
Good Luck and enjoy your blooms!

Mike, is your Gardenia still flowering? Remember, it's not a good idea repotting plants in bud or flower. lol Toni

I am sort of in same situation with mike!! I have never had good luck with gardenia but i picked up another one from HD recently! This one came with lots of buds, healthy leaves..few flowers opened!!! (miracle). However, some leaves are turning black and some are yellow. Plant looks pretty healthy except for the black spots. The pot is so small..i feel like it's root bounded. However, can I transfer the plant to new pot with existing condition? Pot is so small i feel it dries up too quicky. I can't even poke my finger into the pot (i don't feel the soil - just roots). I hope all this makes sense! Please share some of your experiences and knowledge regarding my gardenia. thanks!! =)

Empressiove,
You repot gardenia in the spring as I had posted earlier.
You are probably a little late, but if you are going to repot it, do it now.
If you want to repot it in soiless mix, by Al, on the container forum, visit the container forum and get the recipe that they use for gardenia, or ask.
If you are planting outside, that is a whole different story, since you didn't mention what zone you are in, I am going to assume you are going to repot it.