Anime Your Shirts!
In addition to having the right blend of hot sellers and long term sellers, and planning out your production in advance, another path to boost sales is to have a wide range of uniquely designed, cool products on your store. Real eye catching stuff that fans and t-shirt aficionados won't be able to pass up.
And it doesn't get much cooler or eye catching than Anime.
Anime is one of the most popular and profitable genres in pop culture (think of Pokemon and the Last Airbender). Shirts and products featuring good anime is a huge niche that can generate a lot of sales.
Of course, Anime design is next to impossible for even the most experienced designers. So the best thing to do is to outsource!
On Fiver, you'll find Jalen, superjrock1, a terrific Anime illustrator who has done a ton of work with GTC and other t-shirt and POD designers. For a modest investment, you can get started with a range of hip, anime-d shirts that will really stand out.
Can you think of anyone who could be converted to a cool anime character? Bet you could come up with a great list in less than an hour.
All you need to do is create a Fiver account (it's free!) and reach out to get your project going.