Since you aren't sure, I would start small. 24-36 diapers ,4-6 covers total if you have easy access to a washer/dryer.
If you will use some disposible you could probably get away with 18-24. While you assess.
I never needed a doubler
My kids were never heavy wetters, though they did poop multi times a day. I've been a sahm with a very flexible schedule so I could wash as needed.
Sizing is often crazy. Don't buy ahead. Babies grow at such different rates. I could use gmd yellow prefolds from birth till 10m. On the flip of that, my baby potty trained 1m after I bought sz L covers. You just never know
Especially with newborns you can always grab a hand towel in an emergency
I bought some disposibles for travel and emergencies. Always kept some in each car. I rarely used them and gave them away to friends and family.
Like the PP said, you can only plan so far ahead. Researching cloth, especially prefolds is a VERY daunting task! So this is what we did, just to give you an idea...
I bought 1 dozen preemie sized prefolds and 2 dozen infant sized prefolds. I bought two packs of Snappis because I did not want to use pins. I used 4 covers. When my daughter grew out of preemie sized prefolds, I used those as extra absorbency.
I did laundry about every other day for the first month.
Aside from the pack of diapers we got at the hospital and a small pack I had bought, we didn't use disposables. Using prefolds on a newborn is easier than on a bigger child because they are easier to pack and take up less space. I know though that some families prefer using 'sposies while out.
How long a diaper fits is dependent on the child. Your kiddo may grow out of the smaller sizes quickly or they may grow more slowly. I wouldn't buy too far in advanced though. :-)
ETA: There are organic type disposables on the market. I know Seventh Generations are a good one. So if you were looking for organic disposbales I would try Googling around.
If evil means to be self-motivated, to be the center of one’s own universe, to live on one’s own terms, then every artist, every thinker, every original mind, is evil. Because we dare to look through our own eyes rather than mouth clichés lent us from the so-called Fathers…three cheers for Eve. -...