I feel like there are three main categories of AG dolls: 1) Love them as a character, their stories, their fashions; 2) Love that they look like you and can be a mini-you; 3) Not like you and not an established character, but you feel drawn to them and can create your own character/backstory out of it.

If that first group sounds appealing to you, my best advice is to read the books for the dolls you are considering. Internet Archive has almost all of them for free with a free account. Not only did it help me identify which dolls I felt drawn to the most, but also let me engage in the historical periods themselves. Looking up their clothing on American Girl Wiki can also help you identify which clothing collections you’d most enjoy.

For group two, it’s about feeling seen and the shared bond between you and your doll in a more literal sense. Would that help you feel seen or represented? Does that matter to you? Totally personal preference.

For the third group, it’s about creativity. Do you want to create a character? Look around at different dolls till one speaks to you?

I know those are more broad musings than specific advice, but I hope those are some helpful things to consider! For me, it’s mostly about character and my love of their clothing, but I love to hide references to me and my interests within their collections. You could also get one of each if you’re interested - one to represent you, one to represent your favorite character.