I'm due in 5 weeks and am trying to get everything I might need for pumping ready ahead of time.

I have a Philips Avent Isis single electric pump and have NO idea what I need to have in addition to the pump itself.

I just ordered an "essentials" pack that includes:
- Microwave steam sterilizer
- 2x 4 oz. bottles
- 2x 9 oz. bottles

Do I need more than four bottles?

Should I purchase any additional nipples that are meant for different ages/stages or are different flow?

I'm lost. Please help!