Personally, I get most of my Yellow Scrips through Custom Deliveries. As it cuts out the need to actually go gather materials and is literally just buy stuff from a vendor, make 12 items, get 200+ scrips per item.

Then once you get one of your DoH classes kitted out, there's less reliance on HQ materials so it's faster to go out and farm for the stuff to make stuff in a single day before the Scrip turn ins reset.