If you can get your guild mates to commit to adding relics for platoon units, that's by far the best way to pick up additional points. If memory serves, a single unit placed into a completed platoon is worth somewhere in the neighborhood of 700k points. If you're preloading you can spread your platoon units across multiple phases so you can re-use the same characters for platoons in the next phase.
Don't sleep on platoons - they look very daunting and unattainable at the start but you'd be surprised how quickly you'll be filling them if you can get your whole guild to add relics to just a couple of characters. It adds up to big points and more stars.