Speed is not a technical metric. It is the number of people who leave before they see anything.

Where the time goes

Almost always the same three places: an unoptimised hero image, a font loaded from a third party, and a plugin that runs before the page can paint.

What to measure

Not your desktop score. Open the site on a mid-range Android phone on a mobile connection — that is your customer, and that is the number that matters.

What to fix first

Compress the hero image. It is usually worth more than every other optimisation combined, and it takes ten minutes.