There are many ways to get around in Overthrow.
At game start you will have the option to enable/disable fast travel, this can be used to quickly travel to any Camps, FOBs, Bases and Real Estate that you own, as long as there is a land connection between you and the destination. If the destination is an Airfield no land connection is required.
New in v0.7.8.0
On Normal Difficulty you will not be able to fast travel while carrying a weapon. In your backpack/pocket/car is ok.
On Hard Difficulty you will not be able to fast travel while carrying a weapon or driving an armed vehicle.
Cars and trucks can be acquired at any gas station or you can.. "borrow" any that you see parked in the streets. Stealing cars will most likely set off an alarm that alerts nearby Gendarmerie or soldiers
You can purchase civilian helicopters and aircraft at any airfield you control by using the "Procurement" option in the Y menu while there.
Boats and Ferries
At some jetties in many towns across the map there will be a man who can offer ferry trips at a cost to the major towns. He also sells civilian boats.