so when you first get your wand, you can get lots of different cores. This includes the three Ollivander cores (phoenix feather, unicorn hair and dragon heartstring) but also others, for example, veela hair or coral. But Ollivander said very clearly on Pottermore: 'After much experimentation and research, I concluded that only three substances produce wands of the quality to which I am happy to give the illustrious name of Ollivander: unicorn hair, dragon heartstring and phoenix feather.' Everyone gets their first wands from Ollivander's on PW, so why are more than these three cores available? Yes it gives more variation, but the woods do that anyway - or perhaps wand lengths/flexibility could be added in too?
