I’d recommend using one of the gear calculators (one the includes wheel size) so you can compare the gearing on all your bikes. It makes gearing a new bike quite easy.
My gravel was 42×11-42 (so 1:1 first gear). Using the gearing calculator I decided changing to 38×11-42 would be about right, I then found (on the gear calc) that I could replicate that ratio by borrowing a cassette off another bike with my 42 front (11-46 I think) and did a couple of rides to check before splashing out. It worked, and it also confirmed that an 11-46 does have quite big jumps especially in the lowest gears that were a bit annoying.
I recommend Sheldon Browns gain ratio method.