When it comes to armory I use the 'closet rule', if that is such a thing for hoarders. But basically one item in, two items out. Take a look at your armory and evaluate which items are the easiest to acquire and get rid of those first. If you're already on greens and blues then the next step is getting rid of the ones you like the least.

Other alternatives that might help is purchasing another retainer, and you can also put marketable items up for sale at ridiculous prices so they do not sale. It would be really cool if SE did something with the GC barracks that allowed storage of weapons and armor. I am totally cool with having to visit my GC for such purposes because I honestly don't see them increasing the glamour dresser from 200 anytime soon.