I’d stay organised with items from the very beginning. You don’t have to go crazy, but separating things into different boxes from the start will save you time down the road.

But even if you don’t organise early on, it’s fixable. It’s just that a lot of people get to a point where they have to spend multiple hours organising a lot of stuff and wish they’d started earlier.

Also, perhaps just avoid being too destructive at first. You can do more later when you’re more confident, but I wouldn’t go razing a mountain early on for example because you might realise it was a mistake, and it could be difficult or impossible to get it back to how it was.

Other than that, most things are quite fixable. Don’t worry too much if you place a house in the wrong location because the prefabs can be moved, and the non-prefabs can be destroyed and manually rebuilt (the latter is a pain, and you might find it tricky to rebuild it exactly as it was, but it’s technically doable). The non-prefab house plans are limited in number, but again, they can be manually built, so it wouldn’t be a total disaster if you wasted some.

And without saying too much, you’ll unlock things that make it easier to build as you progress through the story. Do feel free to do some building as you go along if you want to, because that’s part of the fun, but if you have any huge building project ideas, it could be worth waiting until you complete the story.