At the bottom usually. Either that, or you'll need some specific smarts or connections that are sought after. That's how it survives the loss of members. Many are low level and are replaceable, they have no actual knowledge about the high level trade. The high level bosses hide really well and try to stay untouchable by letting others do the dirty work.
From what I understand about Dutch organized crime, if you'd start for yourself, you'd have to fight a turf war and will always be at the top of multiple hit lists.
The safest bet is probably shipping drugs by mail through dark markets. A Dutch guy (SuperTrips) got arrested in Miami a couple of years ago. He sold drugs from his bedroom in his parental home. Was estimated to have earned 385k BTC through this.
If you want to see it at work, you could go to some of the Caribbean Islands. Drug trafficking runs through many of them and you can actually see the impact it has on some communities. In Haiti, I was warned to stay away from packages on the beach (though I didn't spot any). Apparently they throw them overboard near the coast, locals find them and sell them back to drug traffickers for about €50 a kg. This way the traffickers don't need to be directly involved with bringing them to shore.
Hopefully this gives you some info. There's lots of books and documentaries about this stuff too, by ex-criminals, insiders and researchers.