With Canon, my general-photography travel kit used to have 3 lenses, all paired on a FF camera:
- 17-40/4
- 24-105/4 IS
- 70-200/4 IS
I have still retained my Canon gear and use Fuji as my travel kit. Were i replacing my gear, I would have probably settled for comparable fast zooms from Fuji instead.
As it turns out, I have settled on the following 3 lenses: 16/1.4, 35/1.4 & 23/1.4
Quite honestly, i think the 50mm (in 35mm terms) is one of the most over-rated lenses in the history of photography. It isnt wide enough to provide a backdrop to street shots, isnt close enough to be a good close-up lens: it's just a weak compromise that is does neither properly.
Now a 35mm equiv, OTOH... that, to me, is the first prime people should buy (I have deliberately gone with lenses outside my comfort zone for other reasons). The 27mm pancake (40mm equiv) would be a good alternative for someone looking for something lighter/smaller instead.
With the "main lens" sorted, a wide angle is next - super-versatile and useful in oh-so-many-places. The 24mm equiv (16/1.4) is a natural option for someone going the prime route: the perfect wide-angle prime, IMO. For someone who does a lot of landscape, interiors, street/crowded markets, etc., the 10-24/4 could be an alternative here as well.
For the third lens, there are a bunch of options. A short tele would probably be the most useful, or a portrait lens - depending on what one shoots. I went with a 50mm equiv as a way to force myself to play with a lens i am not comfortable with, but i'd much rather have preferred the 55-140 zoom.
For my shooting, an 85mm equiv is useless (I used to own one for Canon and sold it after a few years, having taken <10 shots with it), but apparently a lot of people swear by that as their 3rd lens in a prime-only kit.