Salem

I've seen a guy with 3 walls but 2 gates only... what's the recommendation on gates? stack them like a sandwich?

yes

Someone actually pointed out you should offset them. Since a gate is wide enough for two people, two people can actually attack the same gate at once and get through it twice as fast. However, if the gates are offset by one tile, two people can attack the outer gate, but only one can get to any inner gates.

interesting, wonder if this would make the passage too narrow for carrying objects or pulling a sled through the offset gates?

Haven't tried it personally but I understand its possible to pull a sled through the offset gates, albeit somewhat tricky.

You can carry objects through, but not sure about pulling sleds. If they add wagons or carts or anything like that in the future, staggering the gates like this could* keep you from wheeling the transport in at night.

edit: changed * to make a bit more sense

You can easly manevour with sled through gates(you'll have to go in, stop pulling sled and close doors). You can even pull it in 1,5 tile around corners(not sure about 1 tile spaces )