You'll need handle bars - all useful bikes have them. I like road drops and love the larger diameter, compact drops available now, very comfy.

Saddles ease the pain of the seat post and by preference, I use Brooks leather. These work well because they mold to your rear over time and provide the most comfortable seat you'll get. No need for padded panties but if you're into that sort of thing, you can use all the fancy saddles too.

Wheel rims. Recently, the 23mm width rims have become popular because 23mm tyres produce a similar profile to tubular tyres. Although I haven't used them, the H+Son Archetype is getting a very good reputation.

Hubs. No real need to go beyond the Formula/Novatec level, but you can if you want.

My Hillbrick runs a Miche Express wheelset and I love them. Based on that, I'd suggest the Miche Primato hubs with Archetype rims as a very nice wheelset.

My Hillbrick also runs the Miche Primato cranks and brakes and I love them too. Having said that, there are plenty of options.

You won't go too far wrong contacting Scrod at Retrogression and having a chat with him. He'll not only have all the bits he'll be able to guide you to a balanced set up within a decent budget.

Best of luck with your build ... and as always, it doesn't exist without photos.