I purchased a premium theme with provided sample data (origin page speed very very slow...), used child theme (had CSS @Import issue), had lots external CSS, JS & Image (had lots HTTP request issue) and ....
I had trial and error configured with CloudFlare (Free) and will continue try W3TC others function like Origin Pull & Push CDN and Media Library Import tools.
1. I get both Grade A (Page Speed & YSlow) in Home Page, Blog Page & Shop Page;
2. My Page Load Time ave. below 1.5s for Homepage, ave. below 1.0s for shop page and ave. below 1.1s for blog page;
3. I had GTmetrix's daily automatic e-mail alert monitoring my there (3) main page, so far so gooood.....
4. Google PageSpeed scored 95 for Home Page and Shop Page, scored 93 for Blog Page;
5. And sharing knowledge to my theme community forum too... ^.^
Best and Powerful Web Performance Optimization Plugin