Since you don't really know what you want, may I suggest this.

Buy an older road bike off craigslist, with horizontal dropouts. Ride that through the crap weather until it starts breaking while doing research on what components you like. Buy a set a wheels, crank, chain, cog, etc. when you want to make the jump to a fixed gear. Ride it like that for awhile, and if you like it enough eventually buy a new frame and swap all the parts over.