Save on pets.

Don't get a pet. I didn't say to get rid of your pet because that pet is a member of your family. Don't get one in the first place and avoid all pet support and food costs associated with said pet.

Keep your pet healthy. A sick pet can easily become an expensive pet. Feed your pet properly, keep them at an appropriate weight, provide fresh water, exercise regularly, and make sure they get the shots and essentials they need.

Break apart flea drop packets. A rescue group clued me into this one. Take a small glass bottle with an eye dropper top. (Ours came from cleaning drops that belong to the fish tank I believe. health food stores may also sell them for essential oils.) Purchase the pack of flea drops for the absolute biggest dog available at your store in the bulk packaging. Make sure the jar is clean, then break open and pour the individual applications into your jar. Typically the price is nearly the same no matter the size of the dog and we were able to get 2 years of appropriate drops out of a 6 month package. Here is a much more precise explanation. http://www.starlightbostonterriers.com/fleamedchart.htm

Make your own treats. This can be a super fun and creative hobby as well and a bonding experience with your pet. Here is a nice compilation of biscuit recipes for your dog: http://www.thekitchn.com/cookies-for-canines-homemade-d-135078

Spay and neuter your pets to help limit the pet population and to prevent you from supporting additional unplanned pets.