I kept DS in just a onesie when it was hot, then when it got cooler, a onesie with pants and socks. I really only added more layers (inside the house or car) when his hands or feet were cold. Also, with a newborn, you're probably snuggling her so often that
she'll stay plenty warm. I only swaddled DS at night for the first 8 weeks or so, and during the day when he was napping anywhere but ...