I'm surprised you got it to root in water, in my experience Jades have always rotted when rooting in water and root best when simply left stuck in some dry soil.

In any case, whatever soil you use, you will want a fast draining and porous soil.
Many people here would recommend Al's gritty mix, you can find it on the "Container Gardening" forum under the thread "Container Soils - Water Movement and Retention XI"

Here's the mix I'm referring to:
1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil
CRF (if desired)
Source of micro-nutrients or use a fertilizer that contains all essentials

If you can't get the ingredients listed, you can simply mix normal potting soil with perlite and fine pine bark (1:2:2).

You can pot the cutting at any time. Just don't water it until the roots have developed (several weeks). It's okay for the leaves to become thin and soft.

I'd recommend potting it in a terra cotta pot. The clay is porous and helps prevent over watering by absorbing excess water and allowing it to evaporate more quickly.

jades are very easy, forgiving plants:

1. sun, lots of it.

2. not a lot of it. water when the leaves feel soft and the pot completely dry. If in doubt, wait another day or two. The sure way to kill a jade is to overwater it.

they will turn more red when watered sparingly and given as much sun as possible.

3. for your first jade, try either equal parts of a commercial cactus mix and perlite, or bonsai soil specifically for tropical or succulent plants. you can build your own mix if you get addicted- there's no sense in putting out a lot of money on materials for one plant.

4. Don't overthink: a lot of sun, a little water, porous mix.

In addition to the good advice given above, you'll want a small pot to start, not much bigger than the plant itself & its tiny, new rootball.

Once you put it in mix, don't water as was said above (the fat, fleshy leaves of succulents, hold their own water in reserve, so the plant'll be fine w/out water for a while).

The comment not to water 'til roots have developed is correct, but not helpful to you since you won't be able to see the roots.

So pls. DON'T WATER UNTIL YOU SEE NEW GROWTH, that's the surest indicator that a plant has taken root.

Good luck, read lots around here (by good, helpful & knowledgeable folks) & enjoy!

Thanks for the info. The little guy already had grown roots about an inch-2 inches long in the cup of water and had grown some in the few weeks I've had it. And it doesn't seem to be rotted, but to be on the safe side I filled the cup with some potting soil, pretty dry, to wait until the mix arrives. I went ahead and made a mix of fir bark, turface & granite chips on repotme.com, which I can probably use for my orchids as well.

Should I pot it straight into the dry mix? I know with orchids you are supposed to soak the bark first.

Thanks for the info and I'm glad my ignorance didn't kill the plant yet!

Also, a weird thing, it grew lots of roots out of the bottom two --is nodes the right word? But I noticed a couple days ago it had some mini-roots coming out near the top. The plant piece itself is kind of a sideways "S" shape, and it's the bottom curve near the top where the roots are coming out. If it was laying sideways, that part would be in the dirt also. Is this normal? What will happen to these roots if they don't get planted in the mix?

Jades are tough and wouldn't mind being planted directly into dry mix. Although if the roots are as long as you said, it'd probably be fine if you want to dampen it slightly.
Just don't soak the potting mix before using it. Wait for the plant to put out some new growth and establish roots and then water thoroughly.

The air roots are normal, they'll dry up eventually if they don't make contact with soil so don't mind them.