Of course you COULD, but it's not likely unless you can overcome a number of people's hesitations.

First, the question of "is this person/store reputable or a scam?"

It's difficult to prove you are a real business without a website or something to establish trust with the prospective buyer. You'll need testimonials, a substantial following, or other forms of social proof.

Next, you have to make sure people feel comfortable sending you money. What is the guarantee that you won't just keep it? Once money comes out of your Cash app or Venmo, it's not coming back. When I order something from Amazon, I know that I can talk to a customer service rep in the event that ANYTHING goes wrong. What assurances are you giving people on Instagram that you can offer a comparable experience?

In the end, you're probably making things more difficult for yourself. Use Instagram to promote your products, use the DMs to drive them to a payment portal or store, especially if it is one that is familiar and trustworthy. Consider using any of the existing custom t-shirt and product selling platforms out there.

Let me know if you'd like to discuss this further on Clarity.