I am pretty sure glory means the points you get for doing something good during a match. Things like getting kills, capturing an enemy ghost, capturing a point and any other objective from any crucible match. Depending on the game type, you might get more glory points. I don't think the game tells you how much glory you get for each game, but it should take 5 or 6 games (assuming you are somewhat good at the game) to obtain the 100% glory required for the Call To Arms Milestone event.
