The United States already houses over 20% of the world's prison population while only making up around 4% of the world's population.
We already jail people at a higher rate than any other "first world country". How much more incarceration do we need? If you want to drastically reduce crime, then you have to start at the source. Anything else is just a band-aid solution. Gangs are absolutely a problem and should be dealt with, but they don't emerge out of nowhere, unless you believe black people are just inherently violent.