One advise is not to look too far from home. After all, you just might be able to have a niche that's both practical and popular.
I mean, I would definitely recommend to start with products that we use on everyday level. You can never go wrong with things that you cannot live without.
Here are sample niches that might find helpful to start with:
* Clothing: accessories, plus sizes, maternity, night wear.
* Kitchen: recipes, knife sets, toasters, microwaves
* Beauty: sunscreen, insect repellent, cosmetic & toiletry bags, men's grooming
* Homewares: towels, sheets, rugs, throws, cushions, vases, mirrors
* Special occasion: wedding supplies, party supplies, mother-of-the bride outfits, bridal shoes, birthday cards
* Garden : lawn mowers, gardening tool sets, composter
Let us know if you are still stumped. We will be more than happy to give you a hand.