There’s a glut on what you’re offering. Big design/graphics/display/t-shirt companies that offer a little of everything at deep discounts to keep the prices low, and your margins, too narrow to compete. And you have no network of fans that promote your work. It’s going to be hard to compete with what’s already out there.
So don’t.
Meaning; find a niche market you understand, and service the hell out of it.
For example, specializing in graphics for bands, or for car or boat afficionados, or cigar shops, or tiki bars, or cosplayers… any group with it’s own community, whatever that might be. If you have a hobby or passion with some kind of similar community, I’d start there and try to see if you can make a dent in that market due to your specialized knowledge and understanding of the niche customer base. When they want something made, they will often first try a big existing shop and find that it doesn’t quite have what they want. That’s where you come in.
Just for one example, in the ‘”cosplay” area, there’s a few people out there that do nothing but decorate customized real or replica pilot helmets. Either for real pilots, or for aviation enthusiasts and movie buffs that want something high-quality to display on a desk or shelf. And they make a good living at it, though they might not move many units a year, because they offer a specialized service with a deep understanding of the product, the customers, and the type of art they want painted and taped onto the helmets. And there’s little competition by comparison for what they are expert at. A subset of one of those companies specializes in decorating the protective helmets worn by some newborn babies, to protect their skulls in situations where the cranial bones are too soft or haven’t quite fused yet. An incredibly narrow area of specialization… but there’s a market for it. The decorated helmets look fun and attractive compared to the “medical” looking normal ones. And parents with a kid that has that need, they pay good money for them. It’s not something they can just go get at Walgreens, dig?
There is going to be a useful profit margin in a niche like that, that can’t be serviced by a “normal” graphic design vendor. There are flight sim players out there that pay big money to replicate airplane cockpits. Then there are SCA and Ren-Faire types that might need armor and shields with painted designs on them, that kind of thing… And did you know, there are fine-art painters that paint nothing but portraits of champion farm animal, cattle and race horses for the people that compete in state fairs?
Niche markets. That’s the play, for someone small but agile.