Farming N7 Points
There are two sorts of points one inevitably accumulates by playing: the N7 points, which are awarded for leveling up characters (and figure in the SP campaign as military resources), and Challenge points, for completing various challenges mentioned above.
Now, while the Challenge points always increase, no matter what you play or how (though how fast they’ll increase depends on it very much) – the N7 points can theoretically stop increasing once you’ve brought each of the six classes to level 20. After that, the only way to level them up again (and gain more N7 points), is to promote them, which awards some N7 points in itself, and resets the level for the whole class to 1.
There was a time, long ago, before I discovered the Multiplayer, when the N7 points were the only points, and as such virtually the only measure of one’s success with the game. So people routinely promoted and leveled up their characters over and over again to get ahead on the Leaderboards. Since the onset of the Challenge points, that do a slightly better job at indicating a player’s level of skill and experience, not so many people strive for high N7 scores.
However, I used to be one of them. I promoted my classes more than 80 times in a carefully calculated and definitely premeditated effort to get to a “nice round number”. For example, 13600 isn’t very nice, though it’s certainly nicer than 13620. No, I wanted something with at least three zeros, if not four. Turns out, not every number is on the market; I forget the arithmetic of it now and I might be mistaken, but I believe 20000 is not attainable, while 30000 is. That seemed too long a way to go from the onset, so I had my sights on 18000 – that is, until I unexpectedly landed on 15000 and decided that’s even nicer! So I stopped there.
The most efficient way to farm N7 points is to: 1) play the highest difficulty you can contribute to with your freshly promoted, low-level characters (for me, this was mostly Gold; but I know people who fearlessly take their level 5 characters to Platinum); and then 2) spend pretty much all your credits on the cheapest packs in the Store, the Recruit packs, which are guaranteed to contain XP. People have done math with the conclusion that about two million credits (that’s 400 Recruit Packs) will get all your characters to level 20 from scratch.
Since I was doing this in parallel to trying to max my manifest, I could never spend that much. My process was to play Gold till I got most classes above level 15, then play Platinum till they were all level 20 — and stoically save my credits until I’ve promoted them. Then I’d spend about a million on leveling them up from zero to, say, level 10-12, the rest on Spectre Packs, and consider myself lucky if I got a single black card per cycle.