Answer
It depends on if you are going to exclusively pump or if you are pumping and nursing. If you are exclusively pumping, then DEFINITELY invest in some storage bags. The Lansinoh bags are the best on the market right now. My cousin exclusively pumped with both her boys because neither would nurse, and she had an entire upright freezer FULL of milk by the time they were 4 months old. I would have at least 4 bottles (if you are double pumping) that way you can have two clean bottles while the other two are in the dishwasher. Also make sure you have extra valves/membranes, and some cleaning wipes in case you have to take it on a trip and can't clean it properly right away