Watch a Beginners Guide to Building in Valheim, maybe watch two. No matter how much of this stuff you read here, watching it being done will be way more helpful. Build and repair some stuff and watch them again.

Every one of us does things differently so you will be bombarded by 87,000 different opinions on how and what to build. We are a helpful bunch, if not a bit opinionated.

In the beginning there are huts everywhere to fix up, break down, experiment with. That is a natural way to learn what building elements do. Fix all the broken down houses. Then start building your own after you watch the videos. Just mess about in the meadows and as noted above you always get all mats back (except wood from fire and resin from torches as it is used up). This game does not hold your hand and rewards the curious.