The most important class for me is ALC for Tricks of Trade and Comfort Zone.
Blacksmith for Ingenuity II is great for reciepes at, or above your level (although it reduces effectiveness of Careful Synthesis on lower level reciepes which is strange)
Culinarian for Hasty Touch (don't use without Steady Hands if possible)
Goldsmithing for Innovation (this together with Inner Quiet, Ingenuity II and Great Strides creates some amazing quality numbers)
Weaver for Careful Synthesis I/II (100% success rate and 120% efficiency for Careful Synthesis II are great)

With these, Inner Quiet, Great Strides and Master's Mend I/II and Steady Hand I/II even HQing Twinthread, Darksteel, Rosegold,... becomes rather easy.