Some people say just enough to glue layers together others say about 1/2 inch what do you like and why?
Depends what I am doing, if I am doing a shaped cake like the nesting doll I made I like just enough to glue it together, but if I am doing a cake that isn't shaped or carved I like to put more between the layers. About 1/4 inch thick
I usually do about 1/2 inch. It probably stems from how I like to eat a piece of cake LOL Top layer has the icing.. bottom layer the filling.. best of both worlds. So the filling has to be enough to balance with the cake.
Personally it think it depends on how sweet the filling is. There's nothing worse than a cake that's overfilled with overly sweet fillings. Sometimes less is more. As a general rule, I don't overfill my layers. I think a filling should accompany a cake without taking over the party.
Overall it comes down to personal preference.
Hope that helps
P.S. Don't skim on filling either this can be just as bad as overfilling.