Unfortunately it comes down to many different factors.
Facilities only play a small part in the process and I've often found that you need a high(ish) league and club reputation too, before you can realistically churn out quality regen after regen.
Scotland will always struggle, because it's Scotland. You'll lose out to both Rangers and Celtic on the youth recruitment front, whilst the league is never going to be particularly prestigious.
My advice would be to focus on getting some feeder teams with an emphasis on the ones that generate regens for your side, seek to improve as much of the backroom staff as possibility and keep an eye on other scottish clubs to poach youngsters from.
Depending on time, I might do some research into what factors impact the quality of youth players in a specific league.