Mud or soil (or subsoil) houses are popular, it is estimated that every third house in world is built from soil, earth, clay, mud in many different forms.
One of disadvantage is that mud or earth is not uniform material, practically not possible to prepare standard- that is biggest challenge to understand geological/ geotechnical soil properties to model suitable material properties to meet building standards and norms.. (some info regarding materials properties in paper in my profile)
Water and weathering proof (if applicable) is big challenge too.
What do you mean by using material efficiently? I think that using local material is most eco but not sure about increasing efficiency?
In addition to the helpful response above, I would point out that adobe blocks are made with mud that has a high clay content as well as straw which is mixed in to make the block hold together better. The addition of siding such as vinyl siding on the outside of the adobe bricks will help protect the bricks from weathering. Lighter-weight materials such as tar shingles or plant-based thatch would ordinarily be used for the roof.
In seismic zones, mud has severe limitations. In Perú, we have a seismic design code for adobe blocks (see file attached). Protection of mud blocks can got with large enought roof structures. Quincha is another construction system that combines cane and mud.
By nowm there are several ways to get the adobe blocks protected against the water: some natural polymers extracted from cactus species in mixing water is a good option. You can review some peruvian research on carragenan or cabuya polymers.