Bridge of Sighs is definitely the Robin Trower gateway drug. Every song is perfect. The deluxe edition has stellar contemporary live versions, as well.
Robin Trower Live was the second one I bought, and it adds several great pre-BOS songs to the mix (e.g., Daydream).
After that, it's really a hodgepodge. My personal favorites are In City Dreams and Victims of the Fury, but I'm sure there are some RT fans who prefer For Earth Below or Twice Removed From Yesterday. IMO, Long Misty Days and Caravan to Midnight have good moments but are not representative of his genius.
As for the Jack Bruce albums, I never embraced them. And Back it Up has a welcome dose of Dewar but doesn't have strong songs, again IMO.
Except for the glaring absence of Live, the Chrysalis box set covers all the bases. And you can't go wrong with any of the multitude of live releases from 1972 to 1980, which keep popping out of the Chrysalis vault. Such a powerful live trio. (Don't get me started on the 1980 Fort Worth concert for which I had tickets and was subsequently barred from attending...)