When building a home think about what parts of it are important to you. I really like Bmike's essay/questionnaire idea. What size of living area do you need, and what size do you want? The two may seem like similar questions but they are very different. Make a list of your wants and needs in a new home and clearly define and prioritize them. I think others have covered this much of this portion of the topic, and yes remember both kiss principles. As far as simplifying designs for economy, look to old barns and even old houses. Things like making a two story building with a great room open to the roof with a massive stone fireplace may suit some people, but others might prefer the cozy feeling of a small stove in a room with lower ceilings.
I quite like a standard bent design. Our most cost effective buildings we've built have had the following elements: king posts with ridge beam and common rafters, 1 1/2 to 2 stories(building up is usually more efficient than building out), gable style roof design, and local timber/wood.
I'm increasingly finding the best timber frames are not about the wow factor but more about the warmth and soul of the building.
