My view is somewhat different.
The First Question: to what sort of question are you seeking answers? You might not know this yet, but it’s central.
The First Answer: don’t worry too much about getting this right. You can reorganize later. Tinderbox Is Not A Database. (TINAD!)
Tip: Whatever structure you choose first, take a moment to think about prototypes. It helps a bit to have good prototypes — not unreasonably specific, but also not overly broad.