So I got a nuVinci hub. It is sitting on my desk.

Will probably string it up soon. I'm thinking I'll probably build it into a folding mountain bike, so 26" wheels.

So first off, what size spokes?

Later on, I'm going to be wondering what the best cog ratios to get for it. Off the top of my head I'm thinking something like 44 front and 18 back.

Why? what did it do?

Spokes are easy and hard at the same time. Start by deciding what gauge (most people use 14g) and whether you prefer butted or straight gauge, then use an on-line spoke calculator to figure the length. You'll need hub flange dimensional data, along with rim data, then you can calculate the spoke lengths.

As for sprocket selection, it simply depends on how and where you ride. Everyone has his own philosophy in how to set gear ranges. Mine is to cover the low gear I need, then once that's covered, try to set it up so that my normal level ground cruising gear is 3rd from the top. That leaves me 2 higher for tailwinds, or long shallow downgrades. If you already are riding you should know what rations you tend to prefer, calaculate the gear inches, and use the NuVinci to match that at about 85% of the highest gear.

For a 26" wheel, figure on 1x only, even for 36 spokes. I've only built one of these into a wheel, and that was a 26". Thought I was going to do it 2x but it didn't work. Had to go 1x,, and it turned out fine.
Now that I've said that, check that the new models have the same flange size as the older ones. I know they have changed the hub somewhat.

I can only say what thickness , length depends on the rim you choose. make/brand and model

the 1 X pattern sounds good, basket weaving that cross is unnecessary.

Yes, and all spokes either heads in or out, not alternated.

Passing the spokes all from the same side has the benefit of creating contact and flex at the cross (basketweaving as Fietsbob calls it). That's the good side. However how good depends on how far out the cross is. When too close to the hub, the bending is too much and it causes problems. If so, then normal in/out lacing without interlacing at the cross is preferred.

That's true, but all the 1x builds I've done, even with 20" rims puts the crossing out far enough away from the hub so it's not a problem.

Here's a Rohloff in a 406 rim, 1x, all heads in.

Thanks for the photo. I would probably have built this 1x in/out without interlacing, but can see that your way is fine too.

Have you ever used all heads in or out to help with tension balance on a crossed pattern? I do it routinely with radial, but haven't tried it with crossed.

All in or out, usually isn't possible on any tangent pattern since the spokes get in each other's way. Unless asked I only build radials for the track, and lace elbows out for lateral rigidity (why I went radial in the first place), unless the client says it's a pursuit wheel and he prefers the (slight) aero advantage of elbows in.

My rule is to defer to a client's preference if he gives a reason consistent with the preference, even if I think he's wrong. If his reasoning is inconsistent with the preference, ie elbow in for rigidity, I try to explain where he went wrong, then either do it anyway, or decline the job depending on the situation.