One of your crafting passives will increase the mat return from deconstructing jewelry, blacksmithing, clothing, and woodworking items respectively. Additionally, you get more mats from intricate items.

You'll also get more resources from items that are your level. I often level crating on low level alts by deconstructing max level intricate items and the alts do not get all the resources because they are too low level.

If you need more tempering alloy, you probably shouldnt be deconstructing gold gear. Instead, you want to gather raw ore and refine it. Refining will also benefit from a crafting passive and you'll need to max it for the best chance at getting gold mats. The rough drop rate for gold mats is approx. 1 for every 200 ore.

Other good ways to get more tempering alloy are to run blacksmithing crafting writs - I'm not sure about low level writs, but I get plenty from max level writs. Also, you can max out the blacksmithing hireling passive, who will sometimes send you tempering alloy along with lots of junk.