What c.sam said! And FWIW, I am not all that experienced, but from what I have read here DCS seems to be the most fiddly as far as wiring. Although many have reported good results with many different wiring methods, many others have reported problems.
With that in mind, I will be building a layout soon and plan on following the DCS recommended wiring methods using star pattern and blocks with one power drop per block. Will be using separate power supplies for turnouts and accessories. I'm using Atlas track & turnouts too, have a DCS system and Legacy is on order (will have it if they ever ship).
I'm starting out a bit smaller than you, probably about 6x16 or 8x18, but planning to keep adding on as budget permits. Also want to do the wiring so it can be easily added on to.
To add a little more: Have purchased & will be using OGR's #14 & #16 wire from their online store for all my track power.
