I first introduced bub to formula as the last feed of the day as I found the formula kept bubs fuller for longer and so that meant getting a better nights sleep. I used Nan ha in a medella calma bottle, it's quite expensive but well worth it if you are going to mix feed long term as it makes bubs suck harder for the milk unlike other bottles, and there shouldn't be a problem with nipple confusion. If you are only going to do a couple of feeds per day you won't need to buy to many bottles either. I would also maybe wait a week before introducing any formula to make sure bubs gets all the colostrum at the beginning. I hope that helps and I wish you all the best with becoming a first time mum.