I've always liked to manage lower leagues. The degree of enjoyment is on a whole different level.
But yes, players aren't easy to come by. Money being the key thing... I can ****** maybe 1 or 2 players from the higher league if I offer them a competitive enough salary but that's it. See, usually at the start of my career I set exact expectations for everyone. I tell them I'll get rid of all the unworthy ones. And big signings to me aren't coups. Who cares if the new signing gets ****** of. He'll get over it. When he walks into the club he's just a name, no different than everyone else. Let the pitch prove who you are.
Another thing I do is I select South American databases. Lots and lots of free players! All better then what I have, all cheaper than what I have, all want less money than what I have. And a team like that doesn't need to get redone every time you get promoted. You can stick with a core for a good 2-3 seasons, reinforcing it with 3-4 new signings a year. And I don't get loan, EVER! Yes they may be better than what I have and most of them won't cost me a dime but I just don't do it. I want my players to have a sense of belonging, even though the ax may come down on them at any moment. And I praise praise praise! Keep those spirits up!
There's a lot to be said about a good assistant manager. But I don't look for someone whose job is assistant. I look for coaches or scouts with as good as possible CA and PA ratings, good technical knowledge and determination. But I think that's lately, since I've played for a really long time in all levels and I'm pretty confident I can devise a tactic to suit the situation, so I dont really need the assistant for much more than telling me where I lack and what kind of players I have. That help alone is invaluable to me.
And most of all, I use Genie Scout. Simply because as a lower league team you just don't have the money to send scouts to South American countries to find good players. As with everything else, its in your hands whether to sign a player based purely on Genie's rating or your own careful consideration of his stats.