#1 on my list would have to be the "Bones of a Space". I think , though not impossible, it's hard to have a great space without "good bones". How much interest can a white box have, really? I know that these things really make ones budget go way up, but remember you can add things slowly. You don't have to start with everything the day you move into a house. Layer as you can afford, change is always exciting, at least to me.
Without the wood and the painted brick, what would this space be? Just would not have the same charm, would it?
Elements like built-in bookshelves add so much to a room. Think about you own castle, look around, what could you add?