Overrated beginner mistakes that changed my mind [v2]

For context, I am working with a pretty modest budget so high-end suggestions probably will not land.

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. Looking for honest feedback, not validation.