That all depends on how much you want to buy at once, and how much you want to spoil the pup. (I had all my stuff so my breeder provided just the dog)
• A nice (but not too expensive) bed, as it will probably get torn up before the pup is a year old.
• A food bowl, and 2 or 3 water bowls for where the dog will spend most of the day.
• Nylabone puupy starter kit (3 different styles of nylabones)
• A stuffed animal or two.
• A couple small balls (tennis type or not)
• A crate or kennel (preferably a wire crate with a crate pad to crate train in)
• Talk to the breeder and find out what food it's on and get a small bag of that, and maybe a small bag of a better puppy food if you want to feed them better.
• A regular leash and if you like a retractable one as well.
• A tieout chain or real long lead and maybe a spike for when you go somewhere not offleash dog friendly and want to let them kinda loose
• Some training style treats
• A clicker, if you will be clicker training it.
• A jacket if needed
• Something for the car (changes on how you want to travel. I have a bed with tall sides in the hatch of my station wagon, but you may just need a tiedown for the collar, or something like that)
• Oh, a nice collar is good (I recommend the 'allhoundsapperal' martingale ones as they have lifetime warranties even if eaten by dogs)
• Look around and talk to a few vets to find one that knows of basenjis and who you think will be a good vet
• many more things based on how spoiled you want the dog.