The average small, low key gang will be a lot of 10*'s, possibly with one 20*, who is often the leader, but usually not.
Slightly larger gangs usually have an upper echelon of experienced 20* types. Rarely, they'll have a single 30* in their ranks.
Only very large gangs have more than a small number of 30*'s, and even the largest will have less than ten. They will, however, have quite a lot of 20* members, and the capability to train up most of their less skilled members over time.
Spice consists, almost entirely, of 20*'s and 30*'s, due to their elitist policies.
An example gang, lets say the Skyhighs, would have quite a few 10*'s- The kids from the apartments, the younger members of the gang still learning from their elder brethren. The 20*'s would be the older, more experienced members, plus the occasional talented prodigy, who train the lesser members. Then, there's the Ascended, the small number of 30* grade Punks, including the gang leader and several Punks descended from Lucy, the gangs founder.
In the Tripartite, most of the Gang Leaders are 30* level. Of the champions, they're mostly 30*, with a few 20* level people who won the lesser, but still prestigious, competitions. Of the Aesir, they're all usually 30* level Punks, although sometimes, no 30* will desire the position, so a 20* will take it.