Worst common pitfalls for newcomers [v1]

Not sure if this is the right place to ask, mods please remove if it is not. Spent the last few weekends digging into this and the deeper I go the more questions I have.

Posting this here because the relevant subreddit has gotten too noisy lately. Quick context: I am relatively new to this and trying to find my footing. The trade-offs here are not obvious to me and I keep flip-flopping.