If you can afford it: 3 Mannequins is the only furnitures you need to cap the total storage space for /80 spots. Each Mannequin gives 28 storage spaces. I have 3 mannequins myself but I also have other crap laying around in my MH because they're ex or ex/rare and I don't like to get rid of some of that stuff. Extra rooms would be nice but I don't think people really visiting their nation MH very much anyways. Sadly I don't think most of the playerbase would have use of all those extra rooms unless each room gives some storage space also even if it's a small amount like /20 spaces for a kitchen or /50 spaces for a bedroom.