I eventually got tired of spreadsheets and gathering, so I pumped the breaks on my Island Sanctuary experience. I was probably around Rank 12 when that happened? Then I started spending about 2 minutes at the Island Sanctuary every time I login, and I'm almost at Rank 20. Here's my strategy:

Animals
On days when I login, I collect all the resources from my 20 unfed animals.

Crops
I never water my crops; they only get watered when I drop by while it's raining. When they're ready to harvest, I harvest them and plant new seeds.

Crafting
All I care about is being able to craft stuff without running out of supplies. Months ago I found two related recipes that I seemed to have a lot of the supplies for, and I made a preset that alternates those recipes endlessly. One day per week, I put that preset in every lane for a single day, which when I collect will be enough to get the weekly blue currency bonus. What's the demand for these crafts I'm making? I don't know and don't care.

Auto-gathering
I'm always having my mammet auto-gathering from 2 different locations to keep my supplies up for the Crafting. This also gives me the weekly blue currency bonus for gathering, even though I never gathered. Sometimes I forget to renew this at the right time but it's always fine.

Progression
When new opportunities like upgraded buildings or new areas to gather or new tools appear, do them. Do the upgrades. Go gather 1 each of all the new resources so that your mammet can gather the rest.

That's all it takes to make efficient progress and keep making blue currency profit. It's taken a few months, but I'm almost at Rank 20, and it has taken minimal effort on my part. Hope this helps!