i love gradients/gradient maps!
you can just use them as sky colors, for example.
But when used right as gradient maps, they make everything look so good and saves you a lot of time and grief on comic pages.
if you're using gradient maps, try it this way:
Layer >> New Correction Layer >> Gradient Map...
and change the layer mode to (Color) and i like to keep the effect very subtle at 10~15% Transparency.
Browse through the assets library and download a bunch of stuff to try out : >
these are good free ones to try
hope you find this helpful.