Rough order, not a ladder. Each track moves at its own pace: your chords can be here while your lead playing is still a stage behind. Nothing has to be mastered before you move on.
Eight chords, hundreds of songs.
Open chords ring out with open strings, need no barre and turn up in almost every pop, rock and folk song. Start with Em and Am (two and three fingers), then add the rest. Changing between chords cleanly matters more than how many you know.
Ready to move on when
You can switch between any two of the eight chords about 30 times in a minute, and strum a whole song without stopping.
Songs to try
Knockin' on Heaven's Door
Bob Dylan
G D Am · G D C
Leaving on a Jet Plane
John Denver
G C G C · G C D
Bad Moon Rising
Creedence Clearwater Revival
D A G D
Sweet Home Alabama
Lynyrd Skynyrd
D C G (round and round)
Zombie
The Cranberries
Em C G D
the record has D/F♯; plain D is fine to start
Your first tunes, one string at a time.
Picking single notes trains the fretting hand to land on one string at a time, and a tune you know tells you at once when a note is wrong.
Ready to move on when
You can play Ode to Joy from the tab at a slow, steady pace, without looking for each note.
Name the notes, hear the mood.
Every barre chord and every scale later on is placed by its root on the low E or A string, so knowing those notes now pays off in stage 3. Hearing major against minor is the first thing an ear learns.
Ready to move on when
You can name any natural note on the E and A strings in a couple of seconds, and tell major from minor most of the time.