My recommendation is to get a mid range digital meter meter that will permit the use of multiple probes.� You should get a unit that has the capability for contnuity testing.� That means some sort of buzzer, to tell you that the circuit is conducting electricity.� The digital meter should also display the resistance of the circuit at the same time.
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One addition you will have to make is a 4 - 6 metre extention line for the probe.� This will let you attach the ground end at one end of the circuit being tested and then let you go to the part being tested.� For example, attach the one probe to a wire at the front dash and be able to attach the other end to the rear tail light.� The extension should be made of multistrand copper wire (coated of course).� You want a probe line that will carry sufficient current without significant internal resistance and voltage drop.� I prefer units that have replaceable fuses.� Yes, eventually everyone will blow a fuse or two...� nice to just replace the fuse, rather than the entire meter.
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The probes used should have tips that can be removed and changed, depending on the circuit being worked on.� That will include shielded rubber boots, alligator clips and sharp needle probes.� No use creating more damage by grounding out other circuits while you work.
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You next best friend is the correct wiring diagram for your vehicle/� That also assume the the Previous Owner (PO) documented any wiring changes in the Bentley manual for your vehicle.� I know that you will document all your wiring changes for the next owner.....� 
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Cheers!
Stuart
1986 Vanagon GL 2.1 (with documented wiring changes in the Bentley Manual)