Gauge or scale doesn't matter here - Gravity affects them all in the same way, so the problems of gradients are similar for trains from Z scale to 12" to the foot!
If you must have inclines on a small board, then the best way is to "Split" the incline - for example, for a 500mm clearance, have one line go down 25mm, the other go up 25mm. Keep them as long as possible even if that means the only flat places are stations and yards.
If you do that, each gradient will be halved, all your loco's will pull good trains and the result will also look much better.
example:
possible single gradient 1 in 50: problem for loco's, even pacifics or diesels are really limited in train length.
use a split gradient over same length: result is 1 in 100, and all loco's can still haul nearly as much as on the flat!
Regards
Richard