I am not a fan of one-size nappies. My personal opinion being that they tend to not fit well at the smaller & larger ends of the scale (e.g. gapey legs that don't seal well on a small baby, and builder's crack with too short a rise on a toddler). My preference is for "sized" nappies, they usually fit better for that particular stage, though of course most babies will need at least 2 different sizes from birth to toilet training. (and also there can be quite significant differences in fit between brands).
I started sewing for my kids really early on, so the cost of having sized nappies was pretty insignificant (I could make a pocket nappy for about $6 each - since labour was free of course
). Only basic skills are needed if you think you may want to give it a go!
If you do decide to invest in ready-made sized nappies, keep in mind that although it appears to be a costly "up front" way to go, it will still be cheaper than using sposies. And I hold onto the belief that the more nappies one has in their stash, the better condition they will be in for the next baby or on-selling, so be kind to yourself and have a good stash to help with the washing stress side of things (wet days, sickness, etc).
And my advice as always, avoid buying a lot of one type of nappy until you've given it a good test that it fits your baby well & that it works for your family (e.g. check that Grandmother can actually use snaps and DP/DH can stuff the pockets). Some recommend using sposies on a newborn baby, but I used cloth from birth for my boys (discovered cloth when #1 was 3 months old, so have bad memories of inferior sposies for her
With her pooing up her back all the time, cloth nappies would have been less
So, my personal recommendation;
Hire a newborn/small kit (this should give you a taste of the different systems; AIOs, pockets, fitteds & covers, prefolds & covers, etc), or watch the trading post on here for cheap preloved nappies, or use sposies for the first weeks until you get your ahead around the sleep deprivation, cracked nipples, and finding a rhythm with your new stage of your journey.
Once baby has chubbied up a bit (or not, my boys were never chubby) and you've been able to test various brands/styles, you may wish to invest in a set of one brand, or continue with having a mix of nappies. Just keep in mind that your baby's shape is likely to change a number of times over their nappying days. It's not a problem when they're sposies and you can use up a packet then buy differently, but you don't want that happening if you've both 2 dozen pockets that are supposed to last to toilet training.
Sorry for the waffle, hope it helps