Nook's Cranny is the centerpiece business in the entire Animal Crossing series. No matter which town you start with, this store is always there. This store will supply you with all the materials that you need, at the cost of varying sums of bells, of course.
When starting AC:CF, like the others, Tom Nook, the owner of Nook's Cranny will let you rent out one of his houses. At the beginning of the game you'll need to pay some of this off by working for him and his shop. After that, you have the option to make your h oues even bigger!
This shop sells just about everything you could ask for in the game. It sells flowers, trees, pieces of furniture, tools, carpets, and wallpaper. Nook's Cranny is the first shop that starts in your town, but you can make it bigger by buying a certain amount from the shop. At its current shape, the shop doesn't hold much, but over time it will grow much bigger, and supply much more supplies.