I started with flats and Baby Beehind bamboo OSFM on the newborn setting. Also BGOS on the smallest setting. Ash was 5kg born.
I would get some flats for home, and maybe another 2 newborn nappies for going out? If your at home flats are great at the start, they need to be changed all the time anyways so it's not hard, and they are much cheaper then buying sposies every week until she fits the other nappies you have

Check B4B maybe for some newborn ones?