Hi Enzo,
Anything with fat or protein in it needs enzymes. The general rule many people use (though this may not suit everyone) is one Creon 10000 capsule per 6 grams of fat/protein. I'm not sure what this translates to in oz or different brands of enzymes.
Many cereals, especially muesli, will have fat and possibly protein in it, have a look at the nutritional panel on the back of the pack, it will tell you the amounts and you can adjust accordingly. Chips will definitely have fat (can be quite a lot) so you will need enzymes for that. Bread again will depend on the brand, so have a look at the pack (if it has one). Candy doesn't usually have fat or protein in it so shouldn't require enzymes.
Good luck