You don't say how long your trip was, but yes it can add up VERY fast!
Our trips are generally 5 -7 nights. We use Magical Express and do not rent a car, using Disney transportation for everything (unless we have to leave property). This can take some planning and a bit more time depending, but it seems to work well for us.
We have had groceries delivered but found that we often didn't use it all and it was costing more than it was worth - again depending on how long you are there.
We generally eat breakfast in the room and we enjoy eating at various places in Disney, but much of it is counter service with a few great meals here and there - we also use the Tables in Wonderland discount card (the old DDE). We have been able to use the "food suitcase" approach. Depending on baggage charges and how much you bring this might work for you. Pack, cereals, bread, english muffins (in a shoe box to keep from crushing), granola bars, PB & J, snacks etc. and then purchase milk etc. in the resort store. The prices aren't as inflated as you might think, especially for just a few things.
We also have an Owner's locker. We have a brita pitcher in there along with other packaged things. (Drink mixes, etc.) we take a water bottle with us in the morning when heading to the parks so we don't need to buy one.
After airfare and tickets, it is the food that is our large charge. We don't buy much in the way of souvenirs etc. and if we do we try to use any discount available (
DVC, AP, etc.)
We also make use of the Disney Visa Rewards card through the year and get at least enough for an AP and some defraying of food charges etc. Just charge it to the room, then use the rewards card to pay it off before you check out, leaving anything over your rewards for your usual payment method.
I don't know if any of these ideas help, but it seems to help us.