With Progenitor enhancments there is now an absolutely incredible number of different potential items in the ilvl 262 and 233 category. By making specific variants tailored to certain use cases you can get a much higher price for your items.
For each armor type you will want to look up the most popular specs and which stat combinations they use. Missives to get the correct stat combination will typically cost somewhere between 500 and 1000 gold, but the difference in price between stat variants can be 10-20 000, and a much higher sale rate.
I have gone through every spec in the game to find the list of optimal stat combinations for each armor type, which is summarized below as well as in the linked spreadsheet, including how many specs prefer that stat combination.
The other thing we can optimize is the progenitor enhancements. based on testing the Erratic Genesis matrix is the best one for tank, and can provide as much as 2-3% of your overall damage in m+. For other specs they are mostly similar, in providing small amounts of value. Aealic Harmonizing stones is the best general purpose one, but the avoidance or speed ones, as well as the more utility farming focused ones can all have value.
Pair it up
Obviously we will want to put erratic genesis matrices only on items that have optimal stat combinations for a tank spec, as it is useless for dps and healers. So below you get the full list of combinations that make sense. I’ve also included population data per spec. I gathered this data before the patch, so it may not be indicative of this season. Either way it will give you a break down of what the likely optimal ratio of crafting the different variants are
I have just recently started crafting items according to this list. On Sylvanas, which is my medium population realm the immediate effect was that I was the only one posting the specific stat variants I targeted for cloth gear. This means I can pick my own price. To get sales here you will have to experiment with your normal price, as you will in many cases be the only one with that specific stat variant. Setting it too high might make players just go for a worse stat variant, but you never know how much someone is willing to overpay for something like this.
In general I suggest going by the sale rates for your profession. Rings and necklaces are always popular as getting optimal stat combinations and a guaranteed socket is very good. Outside of that the big stat slots are theoretically optimal, but they do cover tier slots, which does limit the demand. Overall I try to keep everything in stock on Draenor, and I am getting sales across all slots. If you find a slot sells too slow you can just stop crafting and prioritize your effort on the items that are generating big sales.