Too many unknowns.
I would need to know where you are located? If you are in the USA a plethora of 'grass roots' marketing options can and should be considered.
If you run a BIG printing enterprise located outside the USA, it is highly possible your target audience should not be the tax paying consumer.
Or, it is possible you do not print shirts at all and intend to use a POD for fulfillment and all you need it a place to show your designs.
For each scenario marketing embraces a different expected outcome.
Without more information, guesses is all that can be offered. With complete information not only can the venue be identified, but the message, appeal, brand and the all important WHY refined for the best outcome.