You asked
What lens should I buy first?
The site doesn't have a general "first lens" ranking, so the answer depends on what you shoot. Start with the shooting guides and pick the one closest to your plans.
For most people, my advice is to buy a mirrorless body with its kit zoom first, then add lenses once you know what you enjoy. The first camera guide explains why: the body matters less than the lenses you can add later.
If portraits are your main interest, the portraits guide covers fast lenses and good eye autofocus. If you name the camera you're considering, its page lists the lenses that fit it, and I can narrow those down for you.
Written by Claude from this site's pages.