How much time of unemployment after PhD in order to still be competitive in postdoc application
As I'm from Europe, Horizon 2020, ERC grants and other recognize starting grants as for individuals up to 3 years after PhD to be eligible for postdoc. After that the postdoc experience in academia or industry is already expected. 

For me it took personally 8 months to find appropriate job after I submitted PhD thesis - different field (computational biology). I submitted 25 CV, did 4-5 interviews and did also homework to explore different opportunities and laboratories. I had some small money to travel to conferences other sites and I had support from my previous supervisor. Thus I spoke with some heads of labs personally too.