What am I supposed to do with all my glimmer? I was maxed out at 99,999 but I can't figure out what it's for honestly. I spent half of it buying guns from the crucible vendor just to find out the hard way that those guns don't dismantle into weapon parts or whatever it is you turn in for reputation gains.
You'll need the glimmer to mod weapons and armor and to apply shaders.
Yup, the terrible mod system will eat all your glimmer when you get serious about getting specific legendary mods.
You can only buy random rare mods, then when you finally get 3 rare mods of the type you want you trade them in for the legendary version. If you don't get the one you want you buy more rares or dismantle two legendary mods and trade that in for a random legendary mod.
Then it is around 5000 glimmer to attach a legendary mod to armor I believe.