Some useful things you’ll need to know or should set the game up for before you attempt this.
Minor League GM Tips
One thing to know is that if your team is affiliated with a big league club you might lose your better players to promotion by the big club’s AI GM. Actually, that is realistic for a minor league GM.
Another thing. See if you can sign some free agents to minor league deals to fill roster holes.
I suggest cutting ticket prices at your minor league location. It tends to increase attendance which results in more money.
The most important thing to know is that you’ll only be the manager in the minors, not the GM. So, you’ll be handling your lineups and pitching staff, and just about everything else will be handled by your major league GM.
Playing as GM in the minors is very dull, unless you enjoy playing out every game, and you enjoy making your own depth charts and rotations… repeatedly. Every few days, the ML team will mess with your lineup and you have to rework your team. If you don’t mind doing this chore every day, then you might be happy, but it will take a long, long time before you rise up the ranks. I’ve gotten the same result simply by setting my human GM to vacation mode and then running the sim for a few years. I guess you could put in all that time in real time, and then never ever be promoted… that would be something. Again, that’s realistic. Not what I want in my game, though.
I find it’s better to play GM in some non-MLB-affiliated league, say Mexico or Cuba, where player trades and promotions are rare. That way, you can set your team in motion and your GM skill helps or hinders the team, rather than whatever the game AI wants. You’ll still gain credibility as a manager, and can eventually work your way into the Majors that way.