It's a really easy, low-maintainance industry really. Fogcrystal is bursting with the stuff. I don't bother with leather images (my leather gets used for bags, boots, backparks, quivers, gloves et cetera) or metal studs. There's enough quality modifiers involved to run up the value quite quickly. You get a quality modifier from the weaving, the clothesmaking and the dyeing. By aware that there's a certain speed level to the various tasks.
Plant processing gets done the fastest. The thread will pile up.
Weaving is probably the next fastest, although I'm not 100% sure. I always have cloth piled up but that's because I have more looms than clothiers.
Clothier's shop runs at a middling speed.
Milling/Dyeing is the slowest operation, probably because the millers have to have a bag and the seed to do the job, and the Dyers need the cloth and the dye. Twice as many items to fetch. Obviously strategic custom stockpiles could help here.
The pig tails grow underground but only through half the year, but the dimple dye (which makes things midnight blue) grows all year around. If you have surface farming you can plant rope reed (I get the seeds off the Elves), Blade reed (Green Dye), and Hide Root (Red Dye). A herbalist can help find you the first seeds for these crops, or you can just trade for them. There's also the rare and mysterious SLiver barb (a Fogcrystal specialty) which makes black dye.
In spite of the "cave spider silk for the win comment" there's really no difference in price. It's just a different form of cloth with a different method of gathering. The silk has to be collected from a while away but doesn't require processing. It hits the looms as soon as it's brought in.
Similarly, there's no reason why you should prefer rope reed over pig tails or vice versa. In their undyed forms, pig tails are white and rope reed is green.
Hide root is less valuable than the other dyes, and it's use should probably be avoided.
As long as the whole thing is co-ordinated through manager screen, and you start with enough bags, this is a very easy and satisfying industry (it gives the dwarves lots of satisfying acquisitions to make) with minimal resource requirement.
EDIT: Forgot to mention. Milling and Plant processing don't seem to have quality levels, so you can give those jobs to any odd-job droog. Weaving is something you want skilled dwarves doing, but the dynamic changes if you DO have silk. Because weaving also includes silk gathering, and you will want multiple silk gatherers.