Hi,
It is all a matter of personal preference. I find 28 to be the perfect wide companion to a 50-58 mm lens. Any wider seems too extreme to me for general purposes, and too extreme a difference from the 50. And using them becomes much more difficult to me. I also find them to be "gimmicky" if overused. Kind of like "forced drama" in a way.
This being said, I do like to have a super wide and a 24mm for occasional use. For me, these are a 20mm f.2.8 Canon S.S.C. (new to me after ditching my 17mm Canon to look for a 20) and a 24mm f/2.8 Nikkor pre-AI. Since they are lengths I don't use that often, I don't bother seeking out the fast versions. But I do want fixed-length lenses, not zooms. They are small, light, cheap, and optically superior, in general, especially in terms of minimizing distortion. There are some exceptions in terms of optical quality, but not many.
So, I think a good thing to do might be to rent a wide zoom that covers about the 17-40, 16-35, 20-35, etc. range. Rent it over the weekend, keep track of what FLs you are using the most, and what shots you are liking the most.