Hello and welcome to JM!
That is always a fun question for us CDers... "dream stash"... it is fun to think about!

You will get lots of answers I think. Everyone has their own idea of the best diaper.
I think for me, I am fully trained on jellyroll folded and snappied prefolds in the newborn/EBF stage (newborn and small sizes) and would not change that even with unlimited funds, they just work so well for me and on all body types. But, I would get a lot of nice, sized covers. Fleece wraps, Imse Vimse, and Bummis Super Brites mainly, and fleece cocoons or sleep sacks for a newborn. I like a variety of covers for fun and also to help chubby legs not get red marks from the same cover digging in.
Once fully in real sizes and pooping a bit less dramatically, I would try a variety of AIOs and fitteds to find what fit my LO best. My stash would probably be half AIOs and half fitteds, with a few PUL covers and lots of washable wool interlock covers and longies to go with the fitteds. Lots of fun to be had here
Good luck with your fertility treatments!!!