Front-End Performance Checklist 2017
Vitaly Friedman’s list includes a “Quick Wins” section with the web performance things that can’t be ignored. If you aren’t setting caching headers on assets, optimizing images, and gzipping, you’re leaving some huge and easy performance gains on the table. After you’ve covered those, then you can dig into Brotli, OSCP, tree-shaking, and whatnot.
Speaking of which, I should really look into Brotli, OSCP, tree-shaking and whatnot.