Is my idea even decent?

Hello, thank you for the read!
I'm new to T-Shirt design and online selling of said shirts business.
For the last week or so I've been building my site, branding, etc. I loved my idea so much that I didn't put much thought into what is, in hindsight, probably the most important.
While I don't want to share the details, I feel comfortable saying my idea was to sell shirts & designs with Riddles, Clever puns/Jokes about the human mind and decision making, etc. That was the goal for designing products, anyway.
I didn't jump in wallet out entirely, I bounced my ideas off with other people, friends, even some avid t-shirt fanatics. The positive feedback I got was enough for me to decide to go into it.
My problem is marketing. I'm new to using facebook and the likes to market, but I feel confident in understanding how it functions and how keywords, behaviors targeting, etc. But I realized my biggest problem is I can't mentally identify a specific group that would purchase my designs.
I feel as though I picked a niche (the riddles&puzzles part anyway) that doesn't have a well backed community to piggy back off of to get some early sales. I truly believe plenty of people would get a kick out of some of my ideas, but I'm not sure how to narrow those people down by phrase and behavior, or frankly how to market a brand to them.


So I guess I have a few ideas of how to resolve my issue but I don't know which one or if any I should go about doing.
A) Stick to it and have a little more confidence in what I got. Monitor marketing performance and base future designs off of that, more specific demographic.
B)Switch gears to something related to my idea but not the same (as in swap from riddles to, say math or logic games and those fans) and re-design my products to fit something I can more easily define.
C)Get a hold of a more experienced designer/seller and get suggestions on what I could do to improve, or at least rate where I'm at and tell me if I'm good and should focus on marketing and designing instead of doubting my market (tell me to do option A, I guess)



So I guess that's my struggle. I'm second guessing my idea because I'm having difficulty describing my potential buyers. Is this from lack of experience and I really just need to stick to it? Or am I heading down a hill to a pit of burning money and I just haven't realized yet? If so, what's the best way to check if my idea has potential and I just need to find the right way to market it? (other than spending a ton of capital just to realize there's no potential).

Thank you for reading, and your support!