Highly recommend the fishing route. I effectively leveled ALC and CUL to 50 and got the Alembic and Pan of the Luminary for free. Fishing to get ALC / CUL also reduced the monotony of finishing my Rod of the Luminary as there was an extra motivation to fishing along with crafting related breaks.

If you don't want to fish, I would either focus on a) simple, cheap synths you can NPC, b) more complex foods that sell well in the wards, or c) as suggested above, ingredients for high level synths. I hate having to make tomato sauce and would vastly overpay in most scenarios just to save time.