There is really no rush to expand or get more villagers as the invasions scale to population and will be extremely easy with few villagers.

If you set up your first shelters in a tight circle around the campfire, they will all be warmed during winter. You can fit 6-8 shelters this way.

Be careful of terraforming near natural water spots, as they will disappear forever. Build a well on them beforehand and they will stay. Just don't raise the land after or they will get covered up. Also, wells do not get attacked by enemies.

A hunter's hut is very good for a food source that will train your archers too.

The Wooden Altar gives a very good mood boost to villagers who sit by it during their leisure time. But only 3 can use it at the same time, so it can be useful to customize schedules to have leisure at different times.

Cottages when you can afford them allow for 6 villagers to live in without complaint (can fit more but will not be happy). You can also build storages in them, fitting 6 beds and 2 small storages (from the T upgrade menu), good for holding Jotun blood.

You can use tools without the menu buttons by left clicking, like the hoe for instance will level the ground where you aim (usually), useful for if the terraform orders have red squares over where you want to flatten.

Roads are very useful for faster travel and for keeping villagers on it and away from enemies. Consider making one anytime you notice stone is topped off.

The warehouse can be confusing to set up. Once built, you have to stand on it, press B to build, go back to storage, and select a container to place on the warehouse. The containers here will generally hold a great deal more than the other buildings. Also, you can assign villagers here and they will collect items to store here, particularly useful if you have a mine a little far off, or if you want to stockpile firewood for winter.

Note, you do not need all 3 squares to be green when placing the warehouse, just one will be functional, the center.

Building a sled under the storage tab can make gathering much easier for yourself. It can hold 6 large items and many more small and medium items if opened with T.

Clubs and hammers hit harder on skeletons, and bows/knives/swords work better on the rest.

Hedge and watch towers have wall snap points so can be part of a wall.

You can use patrols to direct your forces to defend particular areas. Patrols can be turned on and off as needed. It can be useful to have multiple types set up for different situations like wisp killing on the beach, defense, attacking a wolf den, or left off for training. Here I have 5 warriors defending this tower for an invasion, 2 archers assigned to the tower and 3 from the barracks with a patrol.

The militia feature on the Odin stone just makes the assigned villagers fight if attacked instead of running. Best not to set warriors from towers/barracks as militia because they already have that function. Anyone combing the beach and confronting wisps would be a good choice so they don't run from wimpy wisps.

Anyone who is assigned to work anywhere near an enemy spawn like a wulfar den or cemetary should probably not be assigned to the militia, as they will stand and fight if they get too close and may get overrun.