Cloth Stash advice

Elle • Snap: MochiBunn
Hi! 
My husband and I are expecting our first in Sept. 
I want to go with AIO's but I'm open to other version but I need to learn more of the terminology. 
How large should my stash be? How many small newborn sizes do I need? My family usually has big babies (8+ pounds). I don't know how big my little guy will be but I want to stock up at my shower. 
How many diapers do I really need? We have laundry on site. 
I may use a service the first couple months... 
I don't know what I'm doing. 
Any help, advice, stories would be much appreciated!