Don't repot! That will cause the buds to drop off for sure.
The buds need time to develop before they open, so patience is important. As long as the buds look healthy, you have little to be concerned about.
Gardenias bloom best when potbound and that is why yours is now in bud and why I suggest you not repot.
Here are a couple of things you can do to keep the soil moist. Take the
plant to the sink and let lots of slightly warm water run through the rootball to be sure that it is thoroughly drenched. Place a large saucer under the pot. Water thoroughly as soon as the surface of the soil reaches the point of being just barely damp, but not dry. If this turns out to be every other day, then so be it.
Go easy on the fertilizer at this point. It will not help the buds to open. Miracid is a good choice, but use it at half strength. monthly. Less is better than more