I use cactus soil and perlite or cactus soil and pumice. I also use some bonsai media which I get from a japanese bonsai store, for top dressing, like their kanuma and akadama, or some lava rock. It is a matter of preference. But the important thing is to make it really gritty and very well draining.
I prefer to put my jade plant and other succulents, in a shallow container if possible. Of course if the jade plant is already more mature, it can be placed in a slightly bigger container. Jade plants have a shallow root system as is typical of succulents, and they drink a lot of water during summer. But it does not mean you have to water them often. In my area since we are really in terrible drought conditions, I have to do at least once every two weeks deep watering. But if our temperature forecast is in the triple digits I may do it once a week.
Normally, if I see any of my succulent in declining growth, I inspect the media, are there buggers there or the media for some reason getting too hard. If I am not still certain what it is, to play safe, I remove the soil, wash out the roots gently but allow it to dry out about a day, before I stick it back into a new media.
Looking at the photo you have posted in the other forum..I do agree the media I see there is not the right one. Needs to be grittier than that. And I do not think it is a leaf burn either...more of a manifestation of overwatering. The tricky part is at times over and underwatering shows the same on the leaves. Seeing the media on the photo, I would say the plant got overwatered at some point. The container you are using looks like it is a glazed container, that's okay, but looks a bit too big for your plant, does it have drainage holes? Important to have drainage holes.
You can still save your plant, in my opinion, just change to a grittier soil mix. As mentioned already, cactus soil from the big box stores works, then you can further add more perlite or pumice if you want. Water thoroughly and leave it alone for awhile. Just remove those leaves that are obviously rotting. It will grow new ones when it is ready. Put the plant in a semi-shady area for now, to let it acclimate to its new media. Jade plants can take lots of light, I have them growing outdoors all year long, rain or shine. But we do not have snow here, so I can get away with it. It is an upright growing succulent, follows the light, branching out as it goes. The tricky part with my outdoor jade is during winter, we get the rains, so it is imperative the media is fast draining. Too cold and too wet, is bad for any succulent. Crassulas can take the cold very well, so far they have endured our occasional 21F to 25F, provided it did not rain at that time. If it does, well, for sure I get some damaged leaves later, but the plant quickly bounces back once warmer and more stable temperatures return.
The color of the jade leaves goes apple greenish in color if it is getting enough light, it goes darker green if it is in shade too much, and the growth goes slower when it is in shade. It gets reddish colored leaves when it gets cold stressed during late fall to winter. And if conditions are right, it can also make some cute white blooms, I got mine to have some blooms on just one branch during one winter season.
Good luck, hope your plant recovers!
