Something that might help you, is that blue nodes don't manipulate displacement directly, they tend to use colour information, be that a vector, colour or scalar, which you can then either use as masks or further displace/colour surfaces.
It helps to keep things in the black to white realms, so you can see what's happening at that point in the chain in the nodes preview window. Then multiply up to what ever you need towards the end.
One last quick point, is that the red nodes do a lot and often more than what you can do with blues. It tends to get useful when you have specific requirements for your network.