3mm Automotive wire works fine. I realise you are in the states.. but something like this should be readily available.

https://www.supercheapauto.com.au/p/...60602#start=14

Honestly, the colour confusion is really common - different manufacturers do different colour codings so there is no set in stone rule like 'Black' being the earth. Add to that - there is always more than one way of wiring and it's easy to get muddled up.

It might be helpful if you draw up what you have on paper with the stated colours and post that. Its easier to work out in diagram form for me at least. Then we can draw the connections you need to make to achieve the controls you are after. I'm getting better at it, but I always get someone like Weirdbits, DrNormis or Marcel to check and confirm.

As a general overview, the signal is generated in the pickups and you are trying to control its path to ground via the controls and amp. So all of the earths in the guitar need to resolve to the output jack. The circuit is not completed until you plug the guitar in. It can be helpful just to focus on the hot path through the components first, then worry about earthing everything.

Don't get discouraged, I think my first kit I had about 4 goes at it before I got it working and managed to toast a few pots in the process. All part of the fun.