Will the dog sleep in or out? If it's to be a totally outside dog it' needs a good warm kennel. The one thing we have done with our last two dogs is to crate(so you might want to buy a crate) train them. It means if you need to travel or stay somewhere different with your dog it can be safely and confidently kept in it's crate. Our crates are airline approved so when we fly with the dogs they are somewhere they know. This was also an absolute godsend when my Cairn terrier had to recover from cruciate ligament surgery.
You don't need much for a dog really except lots of patience and spare time for walks. We live where it gets pretty cold so ours have cute little coats to wear if we leave them outside during the day......these are not essential but we find our slightly athritic dog benefit from this.
Have fun and I image the RSPCA might be able to recommend items too.