Here is the ultimate Reccetear strategy: lose on purpose the first week.
You're thinking whaaaa? But get this. First of all, if you lose you get to see the awesome cardboard box ending.
Secondly, if you lose the first week you get sent back to day 2, and your wallet is reset. However, the shelves in the store keep all their items. Just play like normal, but make sure the shelves are stocked with expensive shit at the end of the final day of week 1 when you lose. then you basically get to start week 2 with a huge leap forward. That huge leap will carry forwards exponentially into the future weeks making the game much easier. I ended the 30k week with almost 50k, for example. The major bonus is that it buys you a bunch of extra time so you can go adventuring.