Depends on your people and what you define "design system" as. For most startups I'd highly recommend using off the shelf component libraries so that you don't waste time reinventing the wheel, and have your ux designers use those to assemble bigger patterns that can be reused. (Here's how we list things out, here's our tables, etc). Pick a framework that can easily use your branding colors and fonts, boring tech like Bootstrap, etc can go a long way here.

Developing a "Design System" can be a time sink in the wrong hands though, your people shouldn't be more interested in making that vs your product.