If you are a pet owner here are some tips to help you be more frugal, but first I will tell you some things not to cheat on.
Do not buy the cheapest pet food you find. Typically this pet food is cheap because it contains cheap filler ingredients. When you feed these pet foods to your pet your pet has to eat more food to get the nutrition it needs. As such you end up buying more food in the long run than if your pet was on a good quality pet food. Additionally eating all that junk can cause health problems in your pet, such as diabetes. Cheap filler ingredients include corn, wheat, and by-products (beaks, feet, feathers).
Dog owners can save some money on dog food by feeding the dog human left overs (not table scraps), such as unfinished vegetables (not avocado or onions) and so forth. Some people will even go so far as to actually cook for their dog. This can save money too if done correctly.
Buy Used Pet Supplies
Some pet supplies can be purchased used, at garage sales and such. These should be washed well. Never buy plastic bowls used, in fact plastic bowls should not be used in general, but if you can find stainless steel bowls or ceramic bowls, those are ideal. To be fair stainless steel bowls are not expensive new either.
Cat litter boxes can be purchased used, wash them with a bleach water solution and allow them to air dry.
Dog houses can be purchased used, however wooden dog houses cannot be sterilized so parvo may be a concern.
Carriers and crates can be purchased used, check them for cracks, and make sure all the pieces are there. Wash with a bleach water solution and air dry.
Bird cages can sometimes also be purchased used.
Saving Money on Other Pet Supplies
Owners of rabbits and other small caged pets can save money on bedding by purchasing shavings (aspen is best, pine is okay, but never buy cedar) in large bags.
Large bags of rabbit food can be purchased at a livestock feed store.