Here's a few from my experience:

Low level key skills:
-Rumination, Carpenter 15
When used in combination with Inner Quiet this is a great way to recover CP. You'll get used to staring any craft off with Inner Quiet, and then using Rumination when you're out of CP.

-Hasty touch, Culinarian 15
Basically for when you have durability to spare and are out of CP, it's a 50% shot at gaining more quality.

-Tricks of the trade, Alchemist 15
Handy for those "Good" material phases that come at a time when you can't use them for quality gain. Instead of wasting them, you gain 20CP.

-Careful Synthesis, Weaver 15
For me this pretty much replaced basic synthesis once I got it. You trade a little effectiveness (90%) for 100% chance of success.

Low level less important skills:
-Manipulation, Goldsmith 15
Pretty much Master's Mend, but cheaper. Also takes a bit more skill and planning to use well. Handy if you're a few CP short of squeezing out another quality increase move.