Couple of things;
If you're happy with larger jumps between gears, you can go for a wide range cassette. I find the jumps noticable on an 11-46.
decide whether your low or high range is most important, and go from there. Tune the gearing you have with the chainring size, range is dicatated by the cassette.
FWIW, on 26" wheels, I run a 36 tooth chainring with an 11-46 cassette, and round here (new forest) could easily go up to a 38, although it's mainly irrelevant, as I almost never use either extreme of the cassette.