Your build size, the design, and what you run, has a lot to do with the answer to "how should I wire it" as a big picture. So what can you "safely" buy?
An easy way ro look at things, is to break down cuircuits into systems built separately; track, turnouts, blocks/signals, lighting, accesory voltage(s), etc..
Judging by the use of the word helix alone, I'd plan for buying at least a 12 awg bus wire for each lenth, and 14g drops every or every other piece, or 10 ft max between drops, and assuming you're between 35-50ft max bus length. Another 12g bus, 14g drops run for turnouts/heavy aceessories too; 14 gauge and 16 or less for drops to lights/ small accessories. If you are likely to "grab commons" hastily if adding power the future, beef the common bus feeds up a gauge now. DCS likes a star or homerun type bus circuit, you might consider wiring for it now vs blowing it off as an "I'd never" 
You likely have to jump power over the Ross turnouts and finagle turnout motor selection and control. The systems are not identical so neither is wiring, you'll have to choose there first too.
You had better read up on any possible helix signal issues (try BigBoy; Elliot)
That's about all I have without more specifics.
