I'm a 76+1 Blacksmith- and I have not had very good luck with desynthing backplates and Quadav gear yet. In fact, I can probably count on one hand how many times I've been successful.
If you're 67 I would try
Karimata Arrowheads. They cost a wind crystal and:
Iron Ingot x1, Tama-Hagane x1. Get the Iron Ingots from a guild vendor and then portal outpost out to Norg and sit at the vendor on the dock and craft 'em. you'll pay about 7k a synth overhead. Check into what they're selling for before you start though, when I did it they were about 100k a stack to sell.
As far as sub crafts I'd highly recommend Clothcraft to at least 40 or 50. (You'll want to make the Haubergeon) and Leathercraft is also a pretty solid sub. Obviously in the end you want Goldsmithing-Leathercraft-Clothcraft-Boneworking to 60. But in the meantime Clothcraft and Leathercraft should suffice.
Good luck!