The 4 I use the most:
East Kent Goldings
That set gives you a ton of options. I'd probably go Centennial and Hallertauer next.
I'd much rather have a mix of different kinds of hops than 4-5 similar ones, but that depends on what you make--I'm sure someone on here will want Cascade, Centennial, Simcoe, Magnum, and Amarillo or something like that, and they'll be right for the beers they like.
On deck: Little Bo Pils, Bretta Off Dead (Brett pale)
Secondary: Oude Bruin, Red Sky at Morning (Sour brown ale)
On tap: Saison Duphunk (sour), Amarillo Slim (IPA), Earl White (ginger/bergamot wit)
Bottled: Number 8 (Belgian Strong Dark Ale), Eternale (Barleywine), Ancho Villa (Ancho/pasilla/chocolate/cinnamon RIS), Oak smoked porter (1/2 maple bourbon oaked, 1/2 apple brandy oaked)