Which ones would you recommend getting as a starter set? I am think a 2-stop hard edge, 3-stop soft edge, and a 3-stop reverse grad.
I have read somewhere that wide angles harden the grad edge such that a soft edge becomes more like a hard edge on a wide angle lens. Is this true or greatly exaggerated?
Last question first, yes, it's very true. Looking at it another way, the more telephoto you get the smaller and smaller a fraction of the filter actually gets involved in the shot.
(Aperture and focus distance are also in play. The easy way to think about that part of the equation is this--the more "out of focus" the filter is as a subject, the softer the resulting gradient.)
I use my 2-stop soft more than any other GND. It will bring a lot of scenes to a point where they're in good shape or can easily be worked into good shape in post, it'll (more rarely than any other filter you've mentioned) leave you with an image that doesn't look artificial as a result, etc. The usual advice I'd always heard was to start with 2 soft and 3 hard rather than the other way around.
I haven't used RGNDs, but I'd wonder if the circumstances I'd use them would overlap a fair bit with hard GND.
--Joe