I like to pick "old glory" teams who are struggling a bit atm, such as Aston Villa and Hamburg. These sides have weak and unbalanced squads which need sorting out, but frankly I like having teams which have their own stadiums and chants as it really adds to the character of each match. I love the chants of the Hamburg fans, as they're quite haunting and stimulating.

Importantly to really set these saves apart, I limit myself to no purchases over 10m units (sterling if Villa or euros if Hamburg), focus on the youth academy production (if I have a decent young player in the pipeline, I won't go buying a sexier one from someone else), and I limit nationalities (Brit Isles only with Villa, select Central and Northern European nations for Hamburg). This forces you to really dig deep into the tactics of the game, as you can't use the highly talented players who can overpower the CPU with their OVR's, so you must play to your player strengths and figure out ways to do so. The great side benefit of this is it also makes you much more attached to the players, and really prolongs interest in saves. I'm five years into my current Hamburg save, and my interest has only grown with each season, especially since I now have original starters phasing out and fringe/youth pushing through.

As for settings, I play on World Class on 10 minute halves. The 10 minute halves in particular make a massive difference, as they allow you to slow down the game, be more patient/less rushed, and really sound out those tactics you've dug deeper into with the limitations. It slows down progression tremendously, but is well worth it as you really get into the mechanics of the game. Best decision I've ever made pertaining to CM was making the swap from 6 minute to 10 minute halves.