A bed (borrow if you can, they grow fast), blankets that are washable, towels, industrial strength kitchen roll (the blue one is good which is acquired from work), cleaning spray, poo bags, chew toys, puppy food, two bowls, a secure place to sleep that's easily cleaned - some people use a crate, we use a small room but ensure it doesn't have things they may chew in there eg shoes, piano legs (yes he chewed them) etc. Choose a vet and work out payment for vaccinations, insurance etc. We use vets for pets but as they are a franchise they vary. Investigate training, it needs to happen from day 1, but put down for lessons from around 12 weeks ideally, especially if this is your first dog.
Top tip, let them off lead early, they will be scared to loose you so won't wander - best tip my vet gave me was to do this at 10 weeks.
We are just about to get a second dog so this is going through my mind!