It is always helpful to think of a very small subset of the segment you want to target with your product or message. As small as you can define it. Now paint a picture of this subset of your bigger market. Know everything about this group.
Yes, I know you are worried you won’t have critical mass but don’t worry about that yet. There is time to worry about that later. For now, get every insight about this smallest subset. This insight will get you your core fans and you can always expand later with common denominators, with other subsets of your consumer segments.
How big can it grow?