Serissa Soil

So about a month ago I purchased a serissa start from the conservatory, pink snow rose variety. I brought it home and have just been letting it acclimate to it's new window. It went through a minor leaf drop, but now is starting to grow new leaves and really likes it's new spot. So it's time for me to repot it soon, but with them liking some acidity to their soil i was wondering what soil mix people have used for them. The club mix mixed with a little coffee grounds is what i was thinking, but unsure of a good ratio. What do you guys think?