Do you have an idea of what size you are?
Do you want modern indexed brifter shifting?
How many speeds?
You also need to pay attention to the drop out spacing? is the bike 126 or 130 if you are doing 8 speed and above you want 130 (if it is steel you can either cold set a 126 to 130 or just hand spread when putting the rear wheel in)
Lot's of options....One is find a bike that is your size and equipped the way you want.
Another is find a frame, then if you want modern gear get a full group from a uk bike shop. The C&V for sale section and a WTB gets really good results
Look for double butted tubing and forged dropouts as a basic indicator of mid level or higher
Personally I like the mix of steel frame with modern gear...... at a rough estimate of a really nice build, Frame and fork ...$300 to 500 so call it $400 for what ifs. 105 group from uk bike shop...varies think $450 to $550, call it $500, wheel set $300 ( right now velomine has 5800 105 hubs, mavic open pro, 36 spoke for $219 (works 8 to 11 speed)
Mavic 36h Open Pro Black Rims Road Bike Wheelset 8-11 sp Shimano [741117] - $219.00 Velomine.com : Worldwide Bicycle Shop, fixed gear track bike wheelsets campagnolo super record vintage bike)
so $1200 at an estimate, plus head set if needed and cockpit (seat, seatpost, stem and bars) which can varie widely depending on what you want but call it $1500 for really nice bike that is all your spec