Firstly consider that there are two types of Springer - working and show. Both look different and a worker tends to be high drive (give me a worker any day!)
Start with good insurance- lifetime cover of at least £7,000 with third party liability.
If a puppy then puppy vaccines. If/once an adult consider titre testing to check immunity (Vaccicheck cost the same as a booster, which may be unnecessary) and a worm count ever six months - save worming and flea treatment for if they need it as it's not great for them of the environment.
Food - get the best you can afford. A food that costs more per back may Work out cheaper per meal as you need to feed less. Also less will come out the back end.
Allaboutdogfood.co.uk is good for this and I can PM you done guidelines and research on the dos and don'ts (ie avoid Bakers with any dog but you are asking for the Wall of Death round the living room if you feed it to a spangle).
Essential are leads, bowls, beds, poo bags (I like Beco as they are thick but degradable) and toys.
For the car get something that will secure the properly - at least a crash tested harness but preferably a crate in the boot (Trans K9 are crash tested. Pricy new but can be bought second hand and last a lifetime) or a tailgate guard set up (Barjo are great and also easily available second hand)
Also worth considering the cost of a good trainer (force free), even just to get the foundation behaviour right. Get it right early on, less problem later.
If you are anything like me you'll get into dog sports and there's a whole other world of costs with that! 
(cooling coats, warm coats, leg cooling gel, harnesses, bedding and non-spill water bowls in Car, high protein booster meals on competition days etc)