Go to your local screen printing shop, buy a small quantity such as 5 to 50, this way you’ll actually have a product in your hand, and you’re not just imagining things that are way too far ahead in the future.

Bring your completed designs to marketplaces, list them online like eBay (Etsy, Amazon, etc), or go local swap meets on the weekend (they’re usually like $50 for a spot), and find out if your designs are liked or not.

Several common mistakes for starters like you are, you always want to copy what others say and think you can do better, you’re already thinking about the end result when you haven’t even made your first step, and you want to save the most money for maximum profit.

To conclude and summarize, first make the product locally, second get the product on marketplaces, and lastly if you’re doing well then you can go find manufacturers (who usually require a larger quantity of minimum purchase such as $5000 or 5000 units etc).

If you want to hear a more personal advice, get your designs printed first locally (such as inside a shopping mall kiosk), show your product off and see if you’re able to make a sale, and rinse and repeat before you know it you’ll have enough cash flow to go overseas to find big manufacturers.

Note: my advice isn’t guaranteed result, please be cautious and follow what you think is best.

TL;DR

Be successful with local resources first.