I certainly used a lot of ideas from here to upgrade from my first 4 tap Keezer to my new 11 tap.
Best upgrades were converting to EVAbarrier liquid (4mmID) and gas lines, and duotight fittings, they make lines very manageable.
I found shopping on Kegland is the best for research,videos and products but you can't order from them from the USA. I then discovered Howdybrewer after brewing for 25years. There site is somewhat overwhelming because they have so much stuff but you can enter kegland part numbers and find them easily.
I chose to have three (3) gas manifolds to maximize flexibility, CO2, nitro and beer gas. When calculating hardware I always add at least two additional items to the required amount; you will always find a reason or need for them and in a pinch you will have them on hand.
Below is my current setup but I also have two Nitro taps that were not used for this kezzer load.
I may consider adding a fourth manifold in the future since there is a need for a high pressure and a low pressure Nitro feed and It would be easier and cheaper than a multi gauge.