I always find this a tricky one as we just used Motherease Onesize on Charlotte until she was about 3 months old and I found cloth boards
They worked really well for us and I am still a big fan of onesize nappies as I think they are great value. But I know many people prefer little nappies on a nb and I would probably buy some little ones if I had another despite having plenty of nappies already.
In my demo pack I have a Swaddlebees OV nb, a bimble and a diddy diaper which are just adorable so would probably have a few of those. Jeannette at Tiddlybums has also given me a small one of hers which is really cute. I have a Tots demo pack with some original, bamboozle and fluffle size ones but don't think I would bother with them, maybe a Little Lamb bamboo size one.
So I would probably say to a new starter:
2 Bimbles or Diddy Diapers (I suspect the Diddy Diapers would last longer
2 Swaddlebees OV nb (although these probably wouldn't last very long)
2 Little Lamb Bamboo size 1
3 Swaddlebees OV onesize
3 Green Kids
3 Baby Beehinds Bamboo
That is 18 but 12 should last a while and then they can add some size 2s as the baby gets bigger.
For an older baby I would swap the bimbles and OV for some HH and some more little lambs.
Mmmmm the options are endless.