Indeed, don't use jazberry graqes. You'll need them later on, and they're rare. I think there are a few bushes out there with them, but not many.
Moonsugar is also very rare. It doesn't grow in the wild- you find it occasionally in chests and the like, but the most common way to find it is by buying it off the Khajits that travel with the caravans. Most of the cities have a small camp outside of the gates where you may find three or four of them hanging out. Around three of them can be made in to thieves guild fences, too, so try stealin' your way around the world to get more clues on how to find them.
Briarheart and Fire Salt are also rare-ish, but I wouldn't call them truly rare. Both are found by killing, not by harvesting. The Forsworn Briarheart's are much more common then Fire Atronaches (and they respawn, if you keep doing repeatable quests in that region- go kill Forsworn leader causing a fuss etc etc), but Fire Salts are likely to be found sitting around (almost every alchemy shop has one or two sitting around for you to steal) and in alchemist's inventories.
Snowberries, on the other hand, are everywhere under the sun. Especially the northern sun. If there's snow on the ground, there's probably snowberry bushes nearby. I think there are around six on the path up 1000 steps you do pretty early in the MQ, but they really are almost everywhere you'll find snow. Harvest and enjoy.