These advances will be important sometimes, research them only when you need them the most:
Shipbuilding (Nets and Coracles for early exploration/transportation)
Slave Labor (if you have hills or mountains for mines)
Concrete (Aqueducts)
Agricultural Revolution (Advanced Farms)
Cavalry Tactics (duh Cavalry)
Cannon Making (for bombarding if needed)
Naval Tactics (Ship of the Line)
Explosives (Advanced Mines, terraform hills)
The table below shows the advances needed for each of the "essential" advances above. Note you don't need Communism for Tank Warfare, but the production can be essential if you intend to build Tanks.
