An obvious way to stop immigration is to offer no pathway to citizenship or social welfare, except for the barest minimum standard to keep people safe and alive for asylum seekers. Nobody will come except genuine people in fear of their lives if there is no incentive.
A way to counter gangs will be to take out adverts in immigration hotspots showing the reality of fake asylum seekers - either getting killed trying stupid things, or living in a detention centre environment.
At the moment, there are travel agencies in Africa that take a couple of grand, take your passport and put you on a flight at the airport, and tell you that Europe will give you everything. The reality is and needs to be, somewhat different.