Try to have multiple tools, like two drills, etc. The reason why is because it is great to be able to use two tools at once on the same part. Other than that, it also offers redundancy if a motor burns out(very unlikely though). I'd say, et two battery drills, a high-power wall drill, a bandsaw, mill and a lathe. With these tools, you can fabricate almost any tool that you want.
I don't know if you would classify test equipment under tools, but make sure you have a multimeter.
For electronics testing, I'd suggest a good (and expensive) multimeter, oscilloscope, a battery beak and some psu capable of running the electronics continuously without worrying about batteries. An ATX PSU will do.
An oscilloscope will also help debug motor speed because if you monitor the voltage, the voltage spikes should partially correlate with the motor speed!
Oh yeah. Also, get an encoder. It is good for debugging if your motors are even getting to speed, and if they are good and not toast!
Otherwise, many things are hand tools. Also, make sure the drill has a clutch so you can use it as a screwdriver. It will save time because no one wants to drive screws manually all day
