Buy the best priced complete bike that you can find, like a Kilo TT or Windsor. Seriously, unless you have special needs, like fenders, racks, or ultra-fat tires, these bikes are more than adequate and will last years. Anything better is wasted on a newbie, and I don't mean that to belittle newbies. Bikes like these give you the opportunity to ride without wasting lots of cash. In the meantime, you gain the experience to know what you really want in terms of geometry, componentry, fit, and frame material. Its very likely that you'll end up wanting/needing something different from your initial thoughts. At that point you can begin to build your dream machine.