In my opinion, bottle warmer is not necessary. I prefer using the traditional method which is to heat up the bottle in hot water. If you really want to purchase it, get a pre-loved instead. Baby playmat, you may want to get it after your baby is born coz you might receive it as gifts from family members/friends. For the other items, get it done before you hit 36-37 weeks coz by then, you won't have a lot of energy to go shopping. And you definitely need the steriliser to sterilise all bottles and pump parts before baby is born.