You ultimately want an odd number of willpower and you will take FFF as your second Submerge bonus. Counting drugs and other augmentations, plan accordingly.
Depending on how your ST handles downtimes will matter, too. If you can only buy dice and not spend edge like in missions, you want a value of fade reduction divisible by 4 (4, 8, 12, 16). 16 is reachable with a drug.