I love signing regens. My advice (which has worked for me the past 6 or so FMs) is not to 'look' for regens, make your scouts do it. I have a scout in each continent looking for players with a potential of at least 4.5*, I have the max age at 21 and see what my scouts come up with - they don't disappoint.
Signing the best regens takes time mate, but you'll eventually build up a youth team worthy of any youth set up in Europe. Make sure your youth facilities are the best to accommodate and make requests to the board to increase junior coaching and the youth recruitment network. Also ask the board for feeder clubs to increase the chances of recruiting foreign youngsters - all these factors increase your own youth intake.
Also so I never turn off the agent filters, sometimes I get regens offered to me who have high potentials.