ThreadBear is a merch incubator - a place where you can see if its possible to develop a secondary income off of your content creation. We have been in this business for years and we have tried all sorts of crazy things, but I wanted to take a moment to distill some of the most important advice we have for content creators.
1. You are the brand. If you expect people to want to buy your merch, they need to see you wearing or displaying the merch. Would you buy something from a big name designer who didn't wear their own brand in public?
2. Start small, but start right. There is nothing worse than deciding that you want to offer merch to your audience and then offer crappy merch. People won't forget that first interaction and will probably never purchase from you again. Remember, you don't get a second chance to make a first impression.
3. Find the right company to handle your merch. All you have to do is a simple Google search and you can find all manner of companies that will do merch for you. It will absolutely be on you to find the right company that's a fit for you. They may not (and probably wont be) the cheapest but trading surety for a small bit of profit will be worth it in the long run.
There you have it, half-a-decade's worth of mistakes in 3 small answers.