You're asking about two big issues here.
Re prostitution & kerb crawling - I believe we should adopt the Nordic Model: criminalise pimps and buyers of sex, but prostitutes should are not criminals.
Re drugs. I don't believe in blanket decriminalisation, no. I think there are very good arguments for decriminalising some drugs, like cannabis (the one thing that gives me pause is not wanting to breathe it in on the streets or because a neighbour is smoking it).
Professionals from the criminal justice system, like police, seem to overwhelmingly believe that criminalising many drugs is the wrong approach and that we'd achieve much more in the fight against them by doing something drastic like decriminalisation. However uncomfortable it makes me, I think we should listen to them and give it serious thought.
Decriminalising and controlling the means of production and trade also means that we can levy taxes and I think we could raise some serious money that way - money which our country really needs.
I'd also be interested in exploring whether decriminalisation would enable us to create safer versions of the drugs (not just uncorrupted versions) and better explore medicinal uses (eg cannabis).
But the fact that I think it could lead to some really interesting and beneficial opportunities, doesn't mean I'm in favour of rushing into any sort of decriminalisation. It would need to be very carefully thought through, with a great deal of regulation (something many in business & finance oppose). So...not simple and not clear cut.