My first road bike - build or buy?

If you can, I would build, assuming you can find a straight frame and forks the right size that isn't a Raleigh. The lads from Nottingham used too many bespoke parts that make it difficult to match up bottom brackets etc. with 'standard' parts. Beware too of French frames, some have 'French' threads ( lots don't ) which again can cause grief.

Apart from the frame, a complete groupset will come with everything you need except seat post, saddle, stem and handlebars, and pedals. And bar tape, and steerer stackers.

It should come with BB and cabling, anyway.

Things the frame might come with: seat post clamp and downtube barrel adjusters.

I'd go down the build it route, but then I have for just about all my road bikes
over the years. The golden rule with road bikes is the frame MUST fit. on the
mtb it's not so much of an issue, but the roadie .... ouch. You'll be in the same
position for hours at a time so careful consideration of stack, reach, seattube
length, toptube length, stem length, seatpost (layback or inline) .....

some frames are longer than others, some more upright, some VERY racey.

most nowadays are STI or Ergo style so brake and gear together in one package.
most brakes come as just that ... brakes, no levers.

I'm interested in this approach too, never having built a bike before.

What parts do you need?

OK, I'll take frame, wheels, crankset/cassette/chain/derailleurs, brakes, stem, handlebars, seatpost and even saddle for granted. Also BB (but which depends on frame, and will presumably affect the crankset). Any other gubbins? And if the gearset has brake handles, does that take the place of any that come with the brake set?

A little knowledge is a dangerous thing, which makes me nigh on lethal.