Even if you have design ideas, you may not have "brand" ideas. A lot of kids who start brands think dope designs sell themselves and while that's partially true, there's a full experience we start to want from you after you do your first or second drop.
Focus on the brand and make sure the designs embody the idea of the brand before you start throwing shit on shirts and putting your name on it. You'd be better off as just a graphic designer if you're just doing arbitrary designs.