Am having good success with Functional CSS (AKA Atomic CSS) - specifically Tachyons (can be found at http://tachyons.io ). It makes a very good base for in combination with component based JavaScript frameworks (React, and Vue being my preferred choices).
For a backgrounder, try https://lnkd.in/dK4rA8z
And an excellent initial article describing scalable CSS from the creator of Tachyons:
https://lnkd.in/dGxdRjJ