Build the design system before the screens
If you mock screens first, your design system becomes a documentation exercise. If you build the system first, your screens become composition exercises. Guess which one ships faster.
Junior designers ask: 'Which screen should I start with?' The answer is none of them. Start with the tokens.
Tokens, components, screens — in that order
A new product needs roughly 8 colors, 4 spacing values, 3 type sizes, 2 radii, and 1 shadow to ship a respectable V1. Decide those before you draw a single screen. The screens that follow will fight you less, and the third designer to join the project will be productive on day one instead of day twelve.
The cheat: steal tokens from your favorite product
Don't reinvent. Open the product you most admire, inspect their CSS variables, and use those values as your starting point. Replace them with your own as the brand sharpens. The point of tokens is not originality — it's consistency.