Mother Base

Mother Base is the base of operations for Snake and his comrades, the private military force called Diamond Dogs.
Staff on Mother Base support you in the area of operations when you request it, and various events occur on Mother Base when you visit.
To visit Mother Base, select it as a destination from the [MISSIONS] tab while in the Aerial Command Center.
New features are added to Mother Base as you add staff, extract materials and other resources, and expand its facilities.

How to Expand Diamond Dogs

Any organization needs new blood to grow.
After you extract soldiers and prisoners from areas of operations to Mother Base, they will be persuaded to join Diamond Dogs.
These personnel then become Diamond Dogs staff and are placed in the unit that suits them best.
As a unit's staff increases so does its unit level, adding new features that can aid you in completing missions.
Once your fame (Heroism rating) increases, volunteers will start to join your organization as well.

GMP

Your GMP (Gross Military Product) indicates the economic status of Diamond Dogs.
Ways of gaining GMP include completing missions or selling weapon emplacements and vehicles extracted from the area of operations. Activities such as developing new equipment consume GMP.

Resources

In the area of operations, materials can be found both in a processed form, or unprocessed in shipping containers.
Processed materials can be used for purposes such as developing new equipment, or they can be sold for GMP.
Unprocessed materials can also be obtained through the Base Development Unit's "Materials Procurement" (automatic mining) function. Once these are processed, they can then be used as processed materials.
As the Base Development Unit's level goes up, the amount of materials procured increases and processing time shortens.
When you obtain rough diamonds, they can be converted to GMP.