The wood poles are useful when you need a pole. For example, you can make a simple shelter by lofting a few poles and sticking roof pieces to it. Or you can put a beehive on a pole. Other uses are decorative, as vikings often had poles reinforcing their walls and roofs.
The horizontal poles can be good mounts for banners, spice rack, or other such things that go on the wall but may not fit quite right without a little buffer piece.

As far as building a home, my first homes are usually just refurbished existing homes. Plan to make mistakes and need to redo your home, and also plan to have many homes or at least advanced bases that you can use as you work in different areas.
A home really just needs 4 walls and a roof, the details on that are up to you (and you get more materials and styles and stuff later).
a full home with everything in it needs about 200 square units of space.
you need room for
- crafting stations and their upgrades
- fire / cooking (its a crafting station but because of the fire, you have to plan for smoke and its special due to that)
- bedroom/comfort area (needs to be in range of fire)
- storage
and you may want space outside to grow food, keep bees, and lets just say you need a good bit of space for some outdoor items.
highly recommended: ocean access nearby.
highly recommended: dig a moat or raise a wall around it with the hoe
highly recommended: raise the farmland as well