Check out the page at https://criticalrole.fandom.com/wiki/Media_Chronology .
That shows ALL the Critical Role media releases, including comics, novels, specials, and the main show, in the order they occurred within the universe. Beyond the official Exandrian time line at the top, though, there's nothing official. The order shown has been agreed on by fans but is, of course, always changeable by CR itself.
That said... if you started with C1 my personal recommendation would be to watch it all the way through (and if you're on episode 21 it's about to get REAL good in a few episodes!) then watch "Search for Grog", "Search for Bob", and "Dalen's Closet" (which are basically episodes 116, 117, and 118 of the Campaign). After that, watch any of the specials that appeal to you, or just plunge straight into Campaign 2.