Any advice as a manufacturer trying to sell clothing on Amazon

Hello,

I help run my families clothing manufacturing business based out of LA. With how things are moving in manufacturing business, I decided to start designing our own products (no trademark), but am applying to the amazon brand registry to avoid any copies. I will be branding my stuff for brand recognition and am looking to fulfill by merchant. My concerns are on how to optimize my ability to make clothing. Any tips, tools on how to design stuff that will sell are appreciated.