As player1 said, the biggest problem is slow AI expansion. This is important in the very early game, as factions take over rebel cities to build their economies up. To get around this, play as many turns as you can at the beginning of a campaign without saving/loading (at least 20 turns). If you have a few hours, this should be easy since the turns go quickly early on (not as much city management). Once the game has progresses this far, try to play at least 5 turns between reloads, so city sieges can be resolved. If you micromanage cities, this can be tough, it is best to create a turn pattern, a checklist that you do for every turn that allows you to quickly finish the turn (combat aside). Find ways to quickly step through your cities and troop stacks to give orders.

There was a Ludus Magna thread about this "bug":
https://forums.totalwar.org/vb/showthread.php?t=45860