It's impossible to give you an indication as so much depends on the age, size and breed, plus your own factors like allergies, whether you work etc. Probably more helpful to think in terms of budget headings:-
Microchipping and ID tag (most rescue dogs come chipped these days)
Poo bags.
Insurance is the biggy and don't forget that even if it is cheap when you get your young dog, it will steadily rise as they get older.
Grooming and clipping (for some breeds, but this can really add up if you choose one that is high maintenance).
Annual vet inspection, vaccinations, through the year, regular worming/anti flea/tick treatments. Even if you have pet insurance, it's surprising how you will need to go to vets for minor niggles that are below your insurance excess - things like lumps and bumps, cuts, tummy upsets etc - the sort of thing that might need a course of ABs or a couple of stitches. These add up alarmingly quickly - good idea to have a credit card if you don't already have one. Also, bear in mind that dog will invariably choose a Bank Holiday weekend to be ill, so emergency vet treatment is always more expensive.
Collar, lead, and depending on breed, you might need coats. Plus bed and bowls and brushes/grooming stuff/shampoo.
Toys, balls, squeaky things, Kongs.
Food.
Training (essential) - go to classes and do KC bronze award as a minimum.
Holidays - either a home boarder, boarding kennels. Expensive at peak times like August.
Dog walker if you are out at work - ideally, look for one with Public Liability Insurance and who is CRB checked.
Fixtures and fittings - you might need to get a crate, dog gates for areas of the house, and appropriate, safe arrangements for your car (dog guard, crate in boot, dog safety belt) plus you will need to ensure garden is securely fenced. Sensible to get a pet vacuum cleaner or one with a HEPA filter - with a dog around there is generally more wear and tear, more dirt, and you will need to do more cleaning.