Hello Xth Squad,
This is quite likely to be one of the first trophies you unlock in this game if you do any crafting as you'll need to Strip equipment you no longer need in order to create new equipment for your squad. You can Strip equipment by going to the Academy then Development Lab then Development and finally Strip.
All non-unique items, those with white names, can be stripped to give you Material codes and in the case of weapons and armor, Junk codes (JW for weapons and JA for armor). You can use those material codes to create new items or strengthen existing ones and one of the best ways to get those material codes is to Strip equipment you no longer need. Only the second tier versions or higher of Materials, Plug-ins and Key Tools can be stripped and in these cases you'll get an amount of that item that is 1 tier lower than what you stripped. For example, you strip a MT Metal II, you'll get 10x MT Metal I from stripping.
You cannot Strip unique items which have a yellow name, you can only sell (Deliver) them. Though just a quick tip but I would not sell any unique items since there's a second semester quest that requires random unique items.
If there is anything I can do to make this solution better please don't hesitate to let me know.