Sharing my experience and correcting / adding some things in the guide and the comments.
I went the route of having both mining and jewelcrafting professions at the same time.
Firstly, I would recommend not creating anything until you have passed 25 JC because you will get 25 JC just purely from the sheer amount of prospecting you will do. Gems should be saved until after this so that they’re not wasted.
After 25 JC, go ham and create as many Tier 1 gems as you can until they turn grey, except do not use
any https://www.wowhead.com/item=36923/chalcedony https://www.wowhead.com/item=36926/shadow-crystal or
https://www.wowhead.com/item=36932/dark-jade . Save them all up for the Icy Prisms.
Farming
Cystalised Shadow from mobs was fine and I was able to get a decent number per hour, but the Crystalised Earth was quite slow on the mobs
https://www.wowhead.com/npc=29124/lifeblood-elemental due to their spacing, inconsistent terrain and other mobs getting in the way. After some testing, I was able to farm up 75G for a Frozen Orb (i.e a Crystalised Earth bought from the vendor) from legion mob trash
faster than I was able to get a Crystalised Earth from the lifeblood elementals. YMMV.
Got to 50 JC by creating the rings from the Crystalised Shadow and / or Earth
https://www.wowhead.com/spell=58146/shadowmight-ring https://www.wowhead.com/spell=58145/stoneguard-band . Getting 50 to 75 JC can be done
purely from creating Icy Prisms and
does not require any titanium or alchemy.
Wrath Alchemy
After I was in possession of a juicy number of the coloured T2 gem I was after, dropped mining for herbalism until I had enough to get 75 alch. I definitely went the route of creating
https://www.wowhead.com/spell=53812 from the
https://www.wowhead.com/item=40199 which I found were far easier to fish than the rose things were to herb. Takes you to 15.
From 20-55 I was able to create entirely
https://www.wowhead.com/spell=53905/indestructible-potion . The
https://www.wowhead.com/item=36906/icethorn and
https://www.wowhead.com/object=190171/lichbloom Would spawn frequently, almost constantly, in this area of Icecrown
Doing the loop around the edge and mostly avoiding spiders would usually get at least 1 batch of herbs. I never did more than 1 empty loop before another would spawn again. Highly recommend this spot. Killing the spiders along the route helped as well since their spawn timers were on a few minutes so you'd get a bit of peace while herbing.
Just for reference how RNG may treat you, I ended up with 32 of the colour gem I wanted, but only 18 of another, unwanted gem. Pure luck that it gave me the most of the colour I was after.