Tires: go western
Tubes: ridenow
Rims: XMCS for carbon, DT swiss for alu
Spokes: Pillar or Sapim
Hubs: definitely go chinese with Goldix or Koozer. The Goldix 370 series is my go to for cheap durable somewhat light builds, available in avery option imaginable
Stem: Uno 7075
Handlebars: unless you want some specific shape or carbon, probably cheaper to go western or Uno
Bartape: currently love the Motsuv, thick rubbery and 5$
Groupset: can't beat Shimano offerings on bikediscount: maybe cheaper to get just the levers+derailleur+chain on there and then get a Shimano cassette on aliexpress (unless you want lighter, original Shimano is cheaper and works the best), Senicx crankset or Magene PES if you need power, Wuzei chainrings.
Rotors: the cheap 5$ each Zrace centerlock are perfect, 10$IIIpro if you want lighter
Seatpost: Elita One
Saddle: Ryet the cheap 15$ 180g is awesome, no carbon