How to Make Money
As a general rule, balance is the key to success. If you balance the order of your upgrades a little bit it will propel your profits by a lot.
The weight upgrade is very important as the more valuable fish weigh a lot and the harpoon upgrade make it so you catch them in less hits which helps with OX management.
The deeper the fish, the more valuable so when you access a new depth make note of which fish appear to be worth the most and then prioritize gathering them and upgrading the recipe a couple of levels. I don’t want to give spoilers so this would be the general strategy but there are exceptions.
One exception that wouldn’t be a spoiler, is make sure you can fill you menu with a full night worth of items requested by a party.
I use at least a dive a day if not more gathering ingredients so I can upgrade the recipe a couple of times.