Hate to say it but I reckon a used new bike. If you go out with your mates on modern bikes you will soon wonder why their brakes work and your don't.
Well, I'll take my Tricolor 600's on Mavic open rims over my son's SRAM Red on Zipp 404's any day of the week thanks.
As for the OP: What do you prefer the look of; retro or recently new?
I love the look of some of the modern carbon frames, but my ability and wallet don't share the attraction
I also like to look of bikes from the 80's and 90's and love the style of some of the continental manufacturers, so that's what I ride.
Custom frames can be cheap, but are a minefield, where as more well known manufacturers or bigger custom brands (like Rourke, Mercian etc) tend to be a slightly safer bet.
Have a look in the classifieds and on the bay, and then ask questions here BEFORE you spend any cash.