SinceI started playing I have been buying everything I can even if I don't want it and selling it to try and add it to the catalogue.

Does this actually add everything to the catalogue? Can I then buy them whenever I want? Have I been wasting my money?

@alistercat:

Yes everything you hold is added to the catalog. You can then order most items. Some are not for sale, like gyroids, Gracie furniture, and fortune cookie prizes.

Does Gracie sell furniture that you can't get from Nook? Exclusive content?

the catalog really is for items you sold already but want, lets say you want 4 pillars to make a Zelda style Temple of time. Plus it helps to have a record of everything you own.