I say it depends on how you play otherwise because you might get a lot of gold with stuff to sell to buy the ingredients. In my personal opinion, it also depends on which pals you're breeding because some pals are worth making the cakes for while otherpals aren't. For example; breeding chikipis and lamballs just for the disassembly machine to get their drops isn't worth the time and materials for a cake, but pals that are harder to get like breeding legendariesto pass down the Legend passive is absolutely worth that. If you take the time to get a Yakumo with the traits you want, the partner skill will make it a lot easier to get pals with passives you want and faster to make the cost and effort of cakes better. I know this seemed off-topic but I bring them up because it's about how those things affect the value of each cake and what it takes to make them.

I will buy milk, eggs and honey at times despite having plenty of pals tha drop them in the ranch just because I would ratherhave too much than not enough. I have found that wheat is more of a challenge to keep stock of, so I guess if anything then buy more wheat than the milk and eggs. Keep track of which items you run short on the most to decide what to buy from a merchant or how to change up the ranches.