Another big mistake is walking straight into an overcrowded niche because it looks successful. You see high sales, big brands, and strong listings and it feels like proof that the opportunity is real. What you do not see right away are the thin margins, rising ad costs, and how hard it is for a new seller to get noticed at all. Starting Amazon by going head-to-head with established sellers is one of the toughest ways to learn. The real opportunities are usually quieter. They show up in smaller sub-niches, repeated complaints in reviews, weak branding, or listings that feel rushed and incomplete. Once you start looking at listings this way, you cannot unsee it.