Level up gear before dismantling?
Solution 1:
If you fully level up a legendary weapon without actually purchasing the upgrades you will get twice the amount of Ascendant Energy. You DO NOT need to spend a single glimmer or material on the item.
Basically instead of getting 2-3 you will get 4-6 or something like that. Good if all your weapons are already fully leveled, you can switch weapons before you hand in a bounty.
However this does not work for armour.
Solution 2:
Upgrading a piece of legendary gear will get you a few extra class based material components out of it, but it won't increase the amount of Ascendant materials reclaimed. It will always be 2-3 no matter how many upgrades have been purchased on the armor. You definitely won't get back any of the common materials like spirit bloom and relic iron you use.
For an example, a redditor dismantled a piece of fully upgraded exotic gear and got 5 sapphire wires and 3 shards out of it.
If you get an extra legendary, just trash it without upgrading it. You won't see any return on the XP or materials you spend. By the time you start trashing legendaries, you won't be hurting for the extra sapphire wire or weapon parts. That's what greens and blues are for at that point.
Solution 3:
At level 20+ I turn my bounties in for leveling gear I found in each slot.
For each 5000xp bounty or two 2500xp bounties you can roughly max out xp on one green item.
When you dismantle these items they give you somewhere around double the parts - 3 or 4 instead of 1 or 2.
From my experience I agree with above: don't actually buy/activate upgrades on the items because they don't increase returns meaningfully.
My main gear purples and exotics are either leveled already or getting all the playtime, so its just a nice alternative to exchange xp for mats.
I don't really level blues with bounties, they return 5 or 6 at dismantle but take more than twice the xp to max a green.
When I'm doing heavy grinds on low level content I equip blues and greens to make the xp go somewhere where I can gain from it.