If I had to pare it down to just the ones I use most then it would be:
- 3 that are good for indoors (midweek trainer sessions)
- 2 that are good for outdoors - long distance, etc. Can also cover longer indoor sessions of course.
That covers a mid-volume training plan doing a wash once a week. At a push could also trim down to just 3 pairs and wash on both off days.
In reality I’ve got that plus a load of other bibs that have specific use-cases (cargo, 3/4, tights, etc.) I rarely make it outside more than two days in a row during non-summer conditions, so as long as I have 2 pairs of each to suit any kind of weather then I’m pretty well covered for year-round riding.