Kiinde Twist Breastfeeding products

Hi, I'm a FTM and just trying to make sure to get this whole breastfeeding thing done right the first go around. I was just wondering about the Kiinde Twist breastfeeding products. I'm looking into buying the gift set. I see that it only comes with one slow, medium, and fast flow nipple. Which I planned to buy more. Any suggestions on how many more of the slow flow I should buy for the time being? I have read that it's best for slow flow nipples until the child is 6 months or older. Is that correct? One more thing, are these pouches reusable or should I purchase an additional 40 bags? I have a sterilizing dishwasher, but wasn't sure how they would hold up.