A niche denotes to an interest commonly shared by a certain group. Almost all drop shipping businesses have their own niche. Take advantage of this by identifying if where your niche gets together such as Facebook groups or blog communities. Once identified, join these groups so you can see what your target customers are discussing.
You can be an ambassador to subtly promote your drop shipping business or introduce your products. More effectively, you can act like a real user and place yourself as an expert in that niche.
You can also use the group's social media page to feature your store. For instance, if you are a shoe drop shipping business, send fashion inspiration lookbooks. Ask the group to post them on its page with a credit to your store.