So many list out there and not one of them tells you correctly what all you need in that diaper bag.
really it all depends on how long you will be away from home.
I always kept 2 bags.
A good reason to purchase the big bag that come with the smaller bag.
If your going to be home only for a hr to run errands or a grocery trip you don't need ypour big bag just for that. You can also keep the smaller bag in the car at all times and just bring it in the house for a refill
For you smaller bag:
small baggie with a few wipes
1 rattle or chew toy
You can always make a bottle before leaving that way its there if you need it and ready to go.
now if your going to be gone for a few hours or most of the day:
take along pack of wipes
formula, but get one of those containers that you can put like 5 serving in so you don't have a huge can to lug
outfit and a sleeper
a few rattles or chew toys
now there are a few things you need to keep in the car at all time JUST in case, that way they are there and they don't take up alot of space in your bag.
A shirt for you for spit up accidents
and 2 diapers in case you ever forget your bag or you run out.