Well, I leveled clothcrafting initially because I wanted the glasses to give my mithra that sexy librarian look, so I a bit biased towards the glasses
My opinions on the various GP items.
Fletching:
More or less useless. If you are using fletching for skillups why do you want to make more in one synth? If you are using fletchings for money, more often than not I'd assume that you could HQ the synth in that case, and these are so cheap that I don't see the point in it really. Wind crystals are plentiful, and like 200-500 gil/stack or cluster, so there is not much savings going on there.
Spinning:
I really like this one because I make alot of threads and cloths from the base ingredients, it tends to be cheaper that way and I also farm/harvest/NPC for alot of my items, I rarely buy finished goods off of the AH. Since these synths tend to use alot of Lightning crystals, which are, about 2000-5000 gil /stack or cluster, this does save a bit of gil. This one is really only useful if you craft alot of threads and cloths though.
Cloth Ensorcellment & Cloth Purification:
These I don't know much about, I need to do some more research on them, but I think Cloth Purification is something you should probably get.
There are alot of ingredient items made using Cloth Purification, and these ingredients are NOT up on the AH with any sort of regularity. More often that not it seems that the crafters who make the items with Cloth Purification are making the finished products with them. This could provide you with a nice little niche on the AH for a bit.
For instance, I bought a Blink Band for my Maat fight. It cost me 90,000 gil, and there had not been a Fine Linen Cloth up on the AH for over six months, despite Blink Bands having a very brisk business, and Flax Headbands are mere pennies.
Weaving Glasses, Weaver's Apron, and Gilt Tapestry:
Unless there is one that you really want above all others, I would get Glasses > Apron > Tapestry in that order, mostly because that is the cheapest way to get the +skill, and to my knowledge they all give equal amounts of +skill.
So in summary, I'd get Spinning, Cloth Purification, and the +skill items for sure, maybe Cloth Ensorcellment after all that, and I wouldn't touch Fletching with a 10ft lance, that one just looks like a waste of GP to me.