A simple "emerge <package>" will pull all the dependencies of a given package.
If you think that some dependencies are not being pulled correctly then the fact is that that package is not a dependency. And if something that you think should be a dependency is not, then the big chance is that, more than probably, an USE flag in <package> needs to be changed. But it could also be an USE in a dependency, and not directly in <package>.
If you need to go picking random packages by hand, then you are doing something wrong, and you probably should be rather looking at the output of
and see what's enabled and what isn't.