How small? My small dog is 7kg and costs me £10-15 a month, and she is on good quality food because shite stuff nearly cost her her life (before she came to me).
Stop believing the marketing that everything you can buy in the shops is full of rubbish, and stop believing that kibble is the devil incarnate. There are many ranges in shops varying from cheap and nasty to good quality, and the same principal is true for kibble. To address concerns I've commonly geard as to why kibble is "bad" - no it isn't all sprayed with oil that goes rancid to make it palatable, and it's no more unnatural for dogs to eat food that has been cooked then it is for humans to eat food that has been cooked.
The advantages to buying a good retail branded food are that the food can be good quality, well bajlanced and consistent, and, yes, much cheaper than butternut or whatever equivalent you are on.
Actually read the labels on the back of the packaging, and take the time to find out what the additives actually mean.
Mine is on grain-free James Wellbeloved for small dogs, and, oddly enough, wet food from Aldi ,( a grain free wet 12 pack of trays) because the ingredients and ratios are almost identical to Lily's kitchen trays. She could be on either/or, it's just that I like her to crunch kibble for her teeth health and DH likes to give her wet food in the morning.
She used to be on Tails, and that suited her just fine too. They don't do the wet food grain free or she'd still be on that.