The three most common things that people screw up on are:
1) Tomatoes/tomato plants
2) Spinach
3) Broccoli
All are either toxic or prohibit calcium absorption (not a good thing). If you are introducing a new gutload, let us know, and we can determine if it is toxic or not
Limityour use of grains, beans, and other items higher in phosphorous than calcium (a little can be very good, a lot is not unless you compensate to fix the ratio). Good grain choices are stabalized rice bran and crushed whole barley. Limit use of broccoli, beet leaves, parsley, cassava, watercress, kale, collard greens, spinach, swiss chard, Soy/edamame , bran, buckwheat, almonds, rhubarb, sesame seeds, apricot, figs, kiwi (anything high in phytates/Phytic acid, Oxilates/ Oxalic Acid, Goitrogens). Some is fine, possibly beneficial. Just not as a regular item. Avoid dog food, cat food, fish food, carnivorecare and other prepared foods that are significant sources of animal protien and/or fat and may provide excessive preformed vitamin A / D (a little now and then is okay, but too much can lead to gout and other issues). Similarily avoid/limit milk, meat, eggs, etc.
BTW tomatoe fruit is okay, just not the leaves of the plants