To date I am experiencing with different niches. I think the correct niche depends on where your interest lies. For instance, if money is of concern then it seems that one needs to focus on profit type niches. If one wishes to share or educate then an area of expertise is in order.
One needs to make up their mind as to where their interests are and be willing to accept both nonprofit and profitable results.
A good money making niche recommended is the finance world, but if financing is not your expertise, and writing about it is difficult...well, there's a problem.
If jewelry is your niche and you can only make a small amount of money but you enjoy making jewelry. All I can say is "Hang in there until you discover that piece of jewelry that can be a goldmine for you." Or continue to make and write about jewelry for the enjoyment of the adventure.