Hi there, I leveled my LTW desynth from 160-170 With the Serpentskin Halfgloves of Crafting. They don't give a lot of skill up so it's slow but they are easy to craft and only require 2 Amphiptere Leather and 1 Crawler Silk.
I am now Desynthing Pterodactyl Straps cause the mats are easy to farm and they give good skill ups. They desynth into I,II, and III FC Demimateria so far, low chance of getting dawnborn sand back as well.