I accidentally maxed an FC from 0 to 8 in less than 12 hours solo using level 50 crafting -> Expert Deliveries and made ~200k points.

I was trying to generate a lot of GC Seals for airship mats. Green or blue craftables can be turned in for seals, and GC Seals are usually iLevel * 5.75 but doesn't matter if NQ or HQ. Then I noticed I was also getting FC points, and double FC Points for HQ. I started HQing them all (RIP quicksynth) and got Rank 8 soon after forming.

I used Militia Choker because it was the cheapest on materials, even when farming myself and pretending opportunity cost doesn't exist. The problem was Hippogryph Leather comes from literally 8 spawns in the open world, and they're used for a Hunting Log, so it takes forever and you will upset people when fighting aggressively for drops.

Other options might be better for you, but watch the shard/crystal count. I saw an equivalent helmet until I realized it wanted tons of shards + crystals of multiple flavors instead of just crystals for Militia Choker.