Legendary armor's precursors. Pvp or WvW. If he doesnt change stats, he can upgrade them to legendary. Of course, it is long time journey. But 1 set can be done by 1 or 2 pieces from strikes, 1 2 pieces from precursors. 1 or 2 pieces from archievements. When he starts doing T4, he will get tons of ascended boxes. You can craft exotic Marauder's armor- the insignia recipe is in any crafting vendor's list. It's kinda misleading as it's one of the few HoT stats that doesn't need a map-grind to start crafting. Iirc, you just do a discovery with the usual armor pieces, insignia, and 5 ecto to make the actual armor piece; you don't need an armor recipe.
Salvaging high level exotic gear yields between 0 and 3 Globs of Dark Matter. Using a Master's Salvage Kit, the estimated average is ~0.5 globs per exotic for exotic gear level 68 or better. [1] Using a Black Lion Salvage Kit, the estimated average is ~1 glob per exotic for exotic gear level 68 or higher. [2]
Ascended Trinkets. In general I find LS3 maps much easier to get a load of the materials for. Siren's Reef Landing and Bitterfrost Frontier in particular. You can get the amulet, backpack, 1 ring and 1 accessory from these maps. Dragonfall seems like it might be a good place to get the 2nd accessory and I'll usually just get the ring from I keep 250 in my mats storage and that's it. The rest I destroy. If I ever want to make ascended gear, I can't go through more then that in a day anyway because of the crafting cooldowns, so there's no point in stockpiling. I can just go get more while the cooldown is running.
A large part of the economy today is driven by ascended and legendary gear crafting. If it becomes super cheap to buy and exchange those, there won't be an economy left. Again, I don't want the final gear to be tradeable. Just the crafting components. That's why the title reads " weapon/armor crafting pieces ".