FAQ > STRATEGY > So many upgrades... which are the really important ones?

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If you are building tanks/artillery/drones and have too much money to spend using only a single factory, purchase the Reactor upgrade on the Factory before building a second one. This will let you build units two at a time and is much cheaper than a second Factory.

The HQ has some extremely useful upgrades which apply to all vehicles of a type. In particular, Tank Shields is a MUST purchase because it greatly improves the durability of your Tanks and also unlocks the Overshield special action for Tanks.

If you feel like you are playing in the dark because your opponent keeps shooting down your drones, then definitely try the Drone Dodge and Cloaking upgrades.

Also, most defensive structures have a Shield upgrade. Even if you don't get anything else, this is almost always worth getting. Without shields, every enemy shot becomes permament damage that can only be repaired by spending more money on a repair station.