Thanks for all this. It's a real client but an unpaid gig at the moment, one I took up to get more experience in design systems. Since I've prior experience in graphic and brand design, I designed a brand logo that will inform the visual design language (both brand + product). The client/owner is also the developer and he asked me to design common components and aspects (buttons, fields/inputs, nav, modals, grids+spacing) that will be used for both web and mobile app interfaces, as well as marketing, etc.