(And no I'm not going to tell you to buy in bulk or buy generic brand foods because I'm sure you've already thought of that. But these do help. But don't buy generic Oreos, Cheerios or Dr. Pepper. They just aren't the same.)
Step 1: Put The Dog to Work
So when we heard about the vet school in town looking for blood donors we signed our youngest up. Greyhounds tend to have the universal donor blood type. So in exchange for his blood every few months we get his food, heartworm preventative, flea & tick preventative and some medical care for free. This has saved us a lot of money.
The other upside is the he is getting experience meeting strangers and becoming more socialized. Since he came to us a very shy boy this has really helped him come out of his shell.