Back as promised and I'll try and answer your question wawabear and let you know what we did with our newborn (now 28 months and still happily in cloth).
Unfortunately I can't comment on the range you are looking at as I haven't used it. From taking a look at the Mio range, it seems to be similar to the idea of prefolds and covers that we use, so maybe telling you how many we had of those for our newborn will help. Boosters tend to be extra layers of cotton/bamboo/fleece that you add to increase absorbency, but you're not likely to need that for a newborn. A liner is almost like a thin piece of kitchen roll which makes it easier to dispose of solid waste. You probably do want to buy these.
Cloth nappies are coast effective and more environmentally friendly but how much more really depends on some choices you make. If you go for the cheapest options (terry squares/muslins/prefolds with covers), wash in an energy efficient washing machine (most in the UK are these days) and line dry then your nappies will have minimal environmental impact and you will save a lot of money. If you buy them second hand and/or use them for a second and third child, then you're saving a small fortune. going to the other end of the scale, if you purchase new all-in-ones (say Bumgenius) and tumble dry, them you're saving a lot less money and the environmental impact is only marginally reduced. All-in-ones, anything with elastic and fleece materials tend to fare less well over the years and so won't make it through quite so many children. I will say that, as a poster above pointed out, that fleece does dry quickly meaning you'll be less likely to use your dryer. We use all cotton so I must say that we do occasionally have to put a load in the dryer over the winter.
We've found prefolds are the way forward in terms of cost/durability/effectiveness and they're our 'go to' during the day at home. We have Bummis prefolds and some prefolds purchased from a local cloth nappy laundry which were really reasonably priced and very good quality. We also have quite a few Motherease fitted nappies (all purchased second hand) which are great for other people to use. Our DS has a childminder who doesn’t want to do the prefolds but will happily do the Motherease. This is actually a really important consideration. If you or your OH will be at home with your baby for the years that they are cloth nappies, then you can just go with what you're happy with, if other people (family, child minder etc.) will be doing a lot of care, then you’ll have to have something that they are happy with too. We’ve found that everyone who looks after our DS is happy with fitted nappies (like Motherease) but not so with folding nappies.
How many nappies you start with depends on how often you want to do laundry. For our newborn we had:
18 prefolds type (this included some muslins)
8 fitted nappies
4 pocket nappies
5 or 6 covers
You’ll change nappies 10-12 times a day to start. We did laundry everyday but we only really need to do it every other day.
As for birth-to-potty sets, this really depends on your baby, and unfortunately you won’t know if they’ll work until he/she arrives. A good friend of mine had a newborn and 9lbs 8oz and she had no problem with a birth-potty-set. Our DS was 6lbs 14oz but only 6lbs once we got him home and as he was super, super long his body was more in the scale of a 5lb baby. Birth-to-potty didn’t come close to fitting him until he was a couple of months only. Luckily I’d got hold of some cheap second hand preemie cloth nappies that worked for him, and folded muslins make a good newborn folded nappy.
I second the above recommendation for the Nappy Lady, check out her online videos. She has some on folding and fastening folding nappies if you’re interested. These days you use a cool little Nappy Nipper, no more scary pins. It’s not necessarily straightforward but, if you watch some videos, that’ll give you a head start. Also, as I said, you’re changing 10-12 a day, so what every nappy you choose, by the end of day two, you’re an expert.