Dry food from Lidl is about £7 a bag
Look at the allaboutdogfood site for foods. What brand is it? The Lidl food Orlando gets a shocking 0.1 out of 5 score, look at/click on the ingredients in the food on that site and you will see why.
As Bitey says a puppy needs a diet that provides its complete requirements to grow healthily, a £7 a bag kibble and floor scraps that are not nutritionally balanced to a puppies needs is never going to provide that. You need a good quality kibble suitable for puppies to start with unless you follow a balanced raw diet which I think is certain amounts of meat, offal, bone daily (I don't do raw so not sure if that needs supplements for a puppy, you would need to research this)
Cheap AND good insurance policies do not exist. If you decide to go cheap, and many do, as long as you go with your eyes completely open which may include having access to large sums of money to pay for exclusions (or to pay upfront while waiting to be reimbursed) or being prepared to put to sleep if you cant afford to treat immediately. You might be lucky and your dog will never need a vet, it you want to take that risk as many owners do you need to be prepared for the consequences should they happen. Our dog once had a dire rear, no known reason, took to vets and they kept in overnight and bang we had a £400 bill (we have petplan who paid directly to the vet, but many don't or the vet will not accept and want you to pay immediately and then claim from your insurer).
Another annual cost to consider for autumn/winter is waterproof clothing for you and anyone else who walks the dog. A 30 minute-1 hour walk in wet weather 2 or 3 times a day requires good waterproof clothing and footwear or it will be absolutely miserable for you. Also lots of clean dog towels to dry/clean mud off after.
We do nails with a dremel sander after being recommended on here, I find it much easier than clipping, but your groomer friend might be able to clip nails for you for free/cheap. We don't need to do it often, 2-3 times a year as he wears them down naturally during walks.