I only use advance armor cores for my armors, since there is no difference in level requirements for armor. My impression, though, is that with the introduction of weapon cores, there is a difference in level-use requirements between basic, standard, and advanced. I don't get many requests for weapons but I just got one. How do I determine which core to use for a given level so that I don't make a level 80 gun for a level 20 character? My munitions trader is level 90, so it doesn't matter to me which I use, I just don't want to do any extra work.