What size of slicker do i get for a border collie and when they get older and what orher grooming stuff do i need.

A good breeder will be able to offer all the correct advice on this unless there are any BC people on here.

I suggest you go about finding a reputable bc breeder first and get onto a waiting list and ask them all these questions.

If you arent working your dog or competing in agility or high end obedience then i would get one from show lines.

Hi Peter grooming your puppy will depend on the type of coat he/she has as a smooth coated dog wouldnt  necessarily need the same tools as a rough coated one.

https://pets.thenest.com/brushing-border-collie-5313.html

I hope this helps - assuming you mean a grooming tool, not a coat which a breed like the BC DOES NOT NEED.   Nature will provide as long as the dog isn't coated.