I don’t handle e-commerce yet, but I will throw in my 2¢.
For keywords, there are different search intents to go after....
“What color belt should I wear with blue pants?”
“What size belt do I need?”
“Men’s leather belts”
“Cheapest belt”
“Best men’s belt”
“XYZ brand 36” brown belt”
The above queries are just a few searches related to belts. Some are informational, some are transactional. All the searches may (or may not) be from someone wanting to buy a belt, but their initial search intent is different.
A branded search may have a higher conversion as the person is seeking a specific product. Other searches may be seeking additional information before choosing a product to purchase.
Identity what your competitors are doing and ranking. Is the niche super competitive, what will it take to rank against them?
Are there other products or keywords that you should focus on that are lower competition and easier to convert?
Is your product location specific?
Keyword research tools can help identify opportunities and possibly low hanging fruit to go after.
Any keywords that have some search volume that you can capture are good. There just need to be enough meat on the bone to go after.
Is this site new or established?