Geography is a very good optional subject for UPSC, BPSC and any other PCS Examinations because it is comprehensive and objective in nature which makes it good marks fetching subject. But it also has some cons like it's syllabus is huge and requires a lot of learning power hence it could be disastrous for those who can't learn things quickly and retain for long. It requires a lot of revision and it is also dynamic in nature hence you have to be updated with latest developments happening around you.
You can learn it chapter-wise as given below, Some of them is available right now while some chapters will come in due course of time.
(A). Physical Geography
I. Geomorphology
1. Geological History
3. Sea Floor Spreading Theory
4. Plate Tectonics Theory
5. Origin and Evolution of Earth's Crust
8. Fluvial Landforms
9. Glacial Landforms
10. Karst Landforms
II. Climatology
1. Atmosphere - Structure and Composition
2. Air Masses and Fronts
3. Cyclones and Related Phenomenon
6. Groundwater and Hydrological Cycle
III. Oceanography
3. Ocean Salinity
4. Ocean Tides
5. Ocean Deposits
6. Coral Reefs
IV. Soils and Vegetation
1. Soil Genesis
2. Soil classification
3. Soil Distribution
5. Ecological Aspects of Monsoon Forest Biomes
V. Ecosystems
1. Concept of Ecosystems
2. Man's Impact on the Ecosystem
3. Global Ecological Imbalances
(B). Human Geography
Economic Geography
(C). Geography of India
Political Geography