If you wire it yourself, you should invest in a lot of different colors of wire.
Creating a harness from scratch can be a hair pulling, aggravating, pain in the @$$.
But if you approach it with a Zen attitude it can be a relaxing mental exercise that pays off very well in looks, usefulness, and satisfaction.
I'd start with a roll each of basic black, white, red, and green. Then buy a good 12 or 24 foot of multi-wire cable that you can pull wires from. The kind with 12 or more different colors. That will let you use color coding for left, right, stop, turn, etc., etc..
With good notes the colors will also help when you eventually need to troubleshoot the wiring a few years later.
Run the wires with an eye for rubbing & pinching that may cause a short after a while. As you run each wire use twist ties so you can hold them in bundles that you will later wrap to create an actual harness that can be more easily removed and reinstalled.
Take your time and don't get frustrated. Remember that the engineers probably spent a few months working on the first factory harness.
Be patient, and maybe, you might just find that you are good at it.