Since you like tinkering, do what I did. Buy a cheap road bike off craigslist, with appropriate dropouts and a modern BB shell, and a wheelset (could be had via craigslist also with a cog+lockring) along with a cog+lockring and a chain (and tires+tubes if you don't have extras around). That will be the bare minimum that you will need to get rolling. Your chainline may not be perfectly straight, but if you use an inner ring it will be close enough to get the job done. After you ride that for awhile and see if you like fixed gear, you can start replacing parts at your will. After I rode mine for a couple weeks, I replaced the BB with a cartridge with a shorter spindle to get my chainline perfect. Then over the year I swapped out handlebars, brakes, crankset, seat, headset, and had my frame powder coated. Doing it this way allows you to get a functional fixed gear for a low price, and gives you time to hunt for parts you want/good prices.