It is not really necessary unless you have a huge layout. But the thicker the wire the less drop it will have ad you get further from the power source. 12 or 14 gauge works. See the end of this video:

House wire is often less expensive than the same gauge separately. But some claim that you get interference if you run a different signal next to a coded signal so you might want to separate the dc power wire from the ac signal wires.

Hi there,

I bought a supply of wire last month at https://www.wiringdepot....ire-16-AWG-100-Ft-Spool.
It works very well. I am using red, brown and yellow for the standard marklin colors on my analog section.
I am using green for the catenary.
I am going to be using orange and black in place of red and brown for the digital section
I will be using white for the house and street lights once I get to that stage.
It will be very colorful underneath the tables :)

I am really not to worried about the costs of the wire, Model Railroading is an expensive hobby anyway.
If it comes down to saving a couple of pennies per foot on the wire then it is probably not the right hobby.
Besides, this company has all the colors that I need and is not like Amazon where I need to buy packages with colors that I will never use.

But as usual, this is my viewpoint, you do not have to agree with it.
Enjoy
Tim

I have looked at Home Depot, Lowes and every other hardware store in this area, including Amazon.
They just did not have the selection of colors and the 16AWG that I wanted.
Besides Wiring Depot ships for free, so that helps.
I agree with your other comments, too much work for not enough value.
Thanks
Tim