I have each scout scout 3 countries with my preferred focus (15-23, 2 star CA, 4 star PA, ongoing, transfers, current tactic used) while having no other leagues loaded other than the country I'm in but I do set my database up like @SecondYellowCard suggests so I have all the newgens come through and my scouts are returning a good amount of prospects.
In 4 years they've returned 592 options.