Badges should follow nights, not purchases
A concert achievement is only useful if it marks something you attended: first logged gig, a new city, a venue you keep returning to. Alerts you dismissed are not achievements.
Radar builds these from your diary. Log the show and the milestone can update. Delete the show and the progress should move with it, because the night is the source.
Which milestones are actually interesting
Tenth gig, first festival, five venues in one city, and seeing the same artist twice are the ones people mention later. A badge for opening the app is filler.
Your profile already shows totals for gigs, artists, venues, and cities. Achievements are the same facts with a moment attached. They are not a second diary.
Do not chase them
Logging a show you did not attend to finish a badge ruins the archive. The diary is for nights in the room. Achievements are a side effect.
If you are starting out, log ten real gigs. The early milestones fall out of that without a checklist.