Depends on what automotive vehicle you want to service.
For older cars, a multi-meter and lots of handbooks would work.
Modern cars have lots of BITE (built in test) capability and so you would need diagnostic software and a CAN interface. Plus lots of manuals and standards eg ISO 11898-1
If you want to set up a research centre rather than a service centre, you need to decide your research strategy, and which areas to research. Modern Car electrics, especially with Hybrids and pure electric cars are complex and require many different kinds of skills.
If you want to look at Trucks, then this is a different area again.
If you can be more specific, people will be able to help you more.
A test bench setup for an electric vehicle requires several things, depending on what you want to do. Examples: Roller test bench, battery simulator, electric measurement equippment (V, A, etc.).