An interesting if not odd question. One can clearly have too few magazines, but too many? Not sure what that would entail. OK, 50 loaded mags is too much AND too many.
A standard loudout would not have included one in the gun if you were jumping, but no-one carries the minimum loadout anyway. No ammo -- no gun.
So, I will say that eight is the perfect minimum
number of mags per AR. Why? Six in two pouches, one in the gun, and a spare at home because one of those mags is already, or will be, bad. Of course, you'll want a bandolier too in a pinch. That might be a disposeable one with another 100 rounds on stripper clips and a mag loading tool, for example, or you might want another loaded six mags (plus another spare) in a different type.
15 is the maximum number -- the maximum number shall be 15!