Amazon restricts sellers from selling in various categories (e.g. Grocery, Health and Beauty, Clothing, Watches, Shoes, etc.). Everyone who wants to sell in those categories, naturally, has to apply for approval (or 'ungating').
The cool thing is that if you are approved, you can enjoy (generally) far less seller competition than the default categories you're already approved to sell in (e.g., books, toys, baby, etc.)
Any seller in good standing can apply, but the whole process can be cumbersome (witness this partial screen shot of the spreadsheet I had to submit for approval in clothing, for example. Yipes!)
So I looked to a service like The Selling Family's Category Approval Assistance Service help me and it was pretty effortless on my part. They took care of everything for me, from photo selection, the templates, the application, etc. They just gave me the exact instructions info to submit to Amazon and a few days later I was approved in Shoes, Watches, Clothing, & Jewelry <--click on each link to see their approval email to me.
You too can get The Selling Family's Category Approval Assistance Service and if you're not approved, you'll get a full refund
Good luck, and keep me posted!
P.S. Category Approval Assistance Service service is not required for you to be approved ('ungated') on Amazon. You can apply for approval yourself manually. But I recommend a service because it will save you headaches and hours of time. Here's why: Amazon likes all your materials submitted 'just so', and the files you have to put together and submit can be long, complicated and cumbersome)